I've been carrying one around for a while-- noticed a flat before I even left the house and swapped out the tube.

Got around to patching the punctured tube yesterday and voilà... no goop in the in the little metal goop-tube-- put a hole in the top with the cap and apparently it was just full of air with not a drop of moisture to be had.

No clue how ancient the kit is plus I have another with only unused patches which must be even older.

I've got another tiny unopened kit of glueless patches which is something I've never tried and this kit it's pretty old too-- probably 8 years or more...

Bicycle tubes are so small nowadays... e.g., 18-25-- is it even worthwhile patching one or have they become throwaway items? Now I'm worried about the tube I replaced the flatted one with... it was small and old too-- a 19-25.

Once opened, those little tubes do not last very long. You're better off just going through the whole tube at once once you have to open it.

My personal strategy: I keep new tubes on hand. I flat, I put in a new tube. I hang the damaged tube with 10 of his buddies in his garage. At some point in the future, I intend to patch all 10 of those tubes and return them to service. Reality? I throw all 10 out. I flat maybe a handful of times a year, it's just not that big of a deal to me.

I carry Lezyne self sticking patch kits and keep at home conventional glued patch kits. I replace both about once a year. Even unopened glue tubes dry up pretty quickly. The patches are probably good for decades. I should just buy a container of Rema Vulcanizing adhesive. I have plenty of patches.

I really like the Lezyne patch kits -- they come in tiny envelopes smaller than a credit card and not much thicker. But after several months in hot weather rides the patches tend to get detached from the waxed paper backing and stick to themselves. So while the patches are good for much longer than a year I replace 'em about once a year to be safe. They cost only about three bucks at the LBS.

Raises the question, since there seems to be so many types of 25 presta tubes available on Amazon for about $5 each when purchased in bulk (4 to 5 at a time), any best buy/brand suggestions?

Even unopened ones don't last forever. A buddy of mine used to run a bike shop with his dad. They closed up shop so he passed a whole bunch of repair kits to me. Wouldn't you know it I go to patch a tube one day and found the rubber cement tubes to be empty. All of them. Good thing I wasn't on the side of the road.

Patches don't seem to go bad. I used a large Monkeygrip patch kit for more than a decade until the large patch that was in it was used up cutting small pieces off of it. As to the glue, if you are going to patch tubes at home, buy a 4 or 8 ounce bottle of Elmer's rubber cement. It is the same as what you get in many of the tubes but in an economy size. It's available at Target stores for 2 bucks a bottle. If you are careless and leave the top off too long and it thickens in the bottle, just add a bit of Coleman fuel if you happen to use it. Brings it right back to the original consistency.

I can't tell a big difference between different tubes and brands.

Undersized tubes tend to expand more inside the tire, then when punctured, rarely give a "slow leak". Oversized tubes tend to periodically give a slow leak which is enough for one to get a few miles down the road.

I've gotten a few tubes from Wiggle.
wiggle.com | LifeLine Road Inner Tube | Road Inner Tubes

If you buy 10 of them, they're $1.69 each.

Although, you may have to pad your order with something more expensive (chains, cassettes, brakes, etc) to get free shipping.

Those small tubes of patch glue drying up aren't unique. Occasionally I'll buy those tiny single-serving size tubes of super glue. They never last long unopened either. I'm guessing those end-crimped tubes aren't air tight.

The only tube of adhesive I have that hasn't dried up is an old tube of Shoe Goo that I've had for more than 10 years. I need it once or twice a year and I'm always surprised to find it's still good.

I was going to say that I usually consider unopened tubes lasting forever, but perhaps you're right that a slight manufacturing defect leads to a hole. Or, getting a hole from bouncing around in one's backpack or seat bag.

It never hurts to have a redundant tube, just in case.

Sometimes the gooey stuff will still work, if it isn't completely dried up.