using my common sense, that is how I've used them. Going against the grain of logic, I experimented leaving it on as described. Wanted to know if being lazy could have a benefit. Big whopping nope!

The thread-on adapters are actually a perfect design for the intended purpose. What's not fine are the cheap aluminum ones from China that don't thread on right. Otherwise, the good ones are a breeze to use, it takes only seconds to screw it on, you can both inflate the tire and check the pressure with a standard tire gauge, and when you're done you just take it off, tighten the Presta valve, and you're done.

It literally couldn't be easier. Nearly 40 years of using Presta valves and those adapters, and never had one problem with either a valve or an adapter, anywhere, and that includes home, gas stations, or sitting by the side of the road. Presta is definitely the better design, but it looks like it's too complicated for some folk.

To be clear, when I said "that is how I've used them" means that I loosen the presta, tighten the adapter over the presta, inflate as needed, remove adapter, tighten presta, stow the adapter.

What I was testing out is the adapter's ability to be left on if the presta is left loosened. THAT I DONT SUGGEST.

So, if you're leaving it on the presta you might want to remove it so you dont risk a low or flat tube.

The poor design part is that they take the simplicity of a Presta valve and makes in to a poor Schrader valve. They could be made so that they just slip on to the valve they’d work better.

But, honestly, I’ve been using Presta for over 40 years and in all that time I’ve never run across a bicycle pump that didn’t have the ability to pump both types of valves. Every floor pump and frame pump I’ve ever had had the conversion hardware in the pump head and could be easily converted when needed.

I prefer presta valves as they are smaller and add less weight to the wheel. I have no problems using pumps or CO2 cartridges when I have to pump up my tires, and I like that presta valves come in various lengths, which comes in handy when I have a bike with deep rims.

The valve I most hate is the Woods valve, which most Americans have never seen, but which most bikes here in Japan come with. In Japan they are called English valves. These valves suck donkey *****. They require a special adapter which you must attach to your pump, the valves have a cap which has to be threaded out like a presta valve, the adapter hooks under the valve head, the top of the adapter has an o-ring which seals the top of the adapter to the valve. The adapters like to pop off your pump if you are not careful, and the inside of the Woods valve has a small rubber tube which must be replaced if the valve leaks. The Woods valve is 19th century technology: primitive, inconvenient, and unreliable, yet for some reason Japan is attached to these stupid valves, and many the new Japanese power-assist bikes which can cost thousands of dollars are still fitted with these valves.

I like Presta more, but Schrader works well too. I had some Presta tubes fail at the stem/tube interface though, never with Schrader.

I’ve only ever used the same pumps as for my Prestas. No adapters, no problem. The tips of the valves where they engage the pump are close enough in diameter.
And just like on Prestas, the valve cap can be permanently left off with minimal consequences.
Yeah, that type of valve core wasn’t much fun. Mostly b/c it created a lot of resistance while inflating. Plastic hand pumps could get warm enough to start deforming.
Over here, we have these:
https://cimg9.ibsrv.net/gimg/bikefor...01658b4144.png
We’d call them ”speed valves”, or ”flash valves” due to how much faster inflation went.
If Japan really haven’t discovered these, there might be a business opportunity there for you.
It’s the exact same fit as the tubed valve cores and with the longevity and flow characteristics like Prestas.

+1 to all dabac said.

Yes, the Presta stem sometimes pulls out of the tube but I’ve also seen tons of Schrader fail at the valve stem. The rubber coating fo the Schrader valve gets cut and it won’t hold air. The stem can get cut when the Schrader valve is at an angle in the valve hole of the rim. Sometimes that’s because people don’t install the valve correctly and leave it at an angle and sometimes it’s due to creep of the tube when the pressure is low. Oddly enough, I’ve never seen a Presta installed at an angle or at an angle due to tube creep.

Tube creep has been an ongoing mystery. Like you say, I've only seen it on my Schrader tires. To be fair, Schraders are more likely to be found on lower end bikes, so maybe they're just more neglected. And my one remaining bike with Schrader is the one that gets the most neglected, since it's the daily commuter bike. Also, Schrader valves tend to be found on bikes with wider tires. But still, 'tis a mystery.

The Schrader tubes I've had are metal all the way down, so cutting the rubber coating doesn't affect anything. I think they're a bit stronger just because the base is bigger and thicker, but that's speculation.

I think what it boils down is that either type of valve requires a modicum of care to use, and the failures are so few and far between that it's hard to pin down either root cause or any kind of quantitative reliability. Most of us ride whatever was on the bike when we bought it. "The good is the enemy of the good enough." In my case, Schrader is gradually fading away because my new wheel builds have all been Presta just due to availability of rims.

The Presta and Schrader valves I've seen are attached differently, the Presta has a groove in the metal stem while the Schrader has an integral rubber circle which in my opinion is stronger due to the bigger attachment area. But yes, I've seen Schrader fail due to tire creep. A friend of mine had this problem on his front wheel, braking on descents with a heavy loaded bike. Tried many things but the only way to really fix it was to change the rim.

I prefer schrader but use both. The only valve I have ruined before is a presta because I didn't understand them. I lose air on both of them sometimes when pumping.

Never had an issue with presta adaptors but only use good brass ones with an O ring. The only time I use a hand pump is when I have a flat on the road.

I don't love them, but I don't regard them as a problem, either. In 21 years, I think I have broken ONE. Big deal.

Presta valves
 

I believe Presta valves are used on bicycles because they require a smaller hole in the wheel so do less damage to the structural integrity of the wheel. I have never considered switching!

Presta Valves
 

I have been in the bicycle industry since 1977 and DO NOT like presta valves. I keep having to reach for an adaptor.

I'm the opposite. I hate schrader valves. Presta only.

The most logical reason for using presta valves I've heard was in drag race cars that had little tiny wheels in front. It was possible they could spin so fast that the center valve would depress from the centripetal force and some air could be lost. The presta valve allowed you to lock them shut to prevent this. I don't know if that's true or legend, but it's what I heard :D
A quick google search of images of front drag wheels shows that at least some are using schrader valves with caps.

I don't own any tubeless wheels, so don't know about that. What about deep rims? I've got two bikes with semi-aero hoops and am sure a Schrader stem wouldn't be long enough even if I drilled out the hole(s). I did have to do a 'shade tree' enlargement to fit a Schrader into a Presta rim once, using the tang of a file. Worked fine.

Presta guy here too
 

I keep an adaptor on all my bikes In case needed I even buy the adaptors to match the cables to add some coordination of the bikes color scheme

some like the schrader because they can use them at gas stations to fill up? Found years ago, that few had their compressors or gauges set so that any more than 60 psi could be put into the tyres, which will get you rolling but not good enough on a 32 width tyre or less. Also have found the issue that whatever depresses the schrader valve on your pump to let the air in is problematical in actually pressing it the right amount to let air in and/or causes leakages greater than the rate one can pump it in. So for high pressure bike tyres, presta for me.

increasing rim depth & reducing the rim width will at some point favor or require a presta.

I have been using presta since my I put alloy rims on my Peugeot UO-8 circa 1974. Never ever had a problem. I carry 2 spare presta tubes always. In the old days of 25mm tires is was super easy, with 32s a bit larger, but still small. My first floor pump was a Silca Pista for tubulars, it was Presta only as are my Silca frame pumps. I do carry a brass presta to schraeder adapter as a just-in-case, but never needed it. None of the folks I ride with use Schraeder, and those that had them on hybrids went to Presta.

My floor pump handles both Presta and Schrader valves without needing to change anything. I use it on bikes, my motorcycle, even my car. The biggest problem is with Schrader valves which sink down into the rim and tire when the tube has very little air in it. The nut on Presta valves prevents that from happening.

Personal Preference
 

Interesting discussion. I have been riding bicycles both on and off road for about 60 years. At 74, I still ride about 1000 miles a year - in Minnesota (with roughly 7 decent weather riding months). I now ride long wheelbase recumbents for comfort (Easy Racers). I have managed and worked in bike shops, and was the president of a large (about 1500 riders) bike club for a couple of years. I have used both Schrader and Presta tubes for those 60 years. For most of them I used only Presta. Still do. Why? Generally, better Presta pumps available. Much more reliable fills with less leakage. Less failures around the base of the stem. And, Presta is what I am used to. My recommendation - go with whatever you like. There was once an article in a magazine called Bike World. The owner of a bike shop related the story of bike rider customers sitting around his shop discussing different brands of components. At one point, they asked the owner what he thought. His response was "quit sitting around talking." "Go ride your bikes." Schrader? Presta? I say Presta.