As StanSeven said usually they do not bother too much, because it is not they who suffer from that. But if you are sure that you cannot test it better, than my questions about pumping should be considered.

Another thought. Check the source of the tube flat. If the hole is away from the road surface and towards the rime itself, the problem is with the wheel. Either it's a rough edge or the rim tape isn't covering a spoke hole. Since you said this happened when new, I bet it's due to rim tape not properly applied.

I had similar problem once. And after several weeks of suffering (i ride every day), i manage to find the hole in the tube, but did not find anything wrong with the tire nor rime, a new tire did not keep pressure neither, and probably after one month of pumping every day, i found i little wire in the tire that punctured the tube very gently :).

That's correct, but first chesterv needs to find a hole :)

On the off-chance that an LBS has been replacing your tubes, and you've somehow pissed someone there off, and that someone is extremely petty, make sure your valve cores are properly tightened. We'll assume this is not the case.

Then they have a leak. If it happens with new tubes, whatever is puncturing the tube is still in the tire (or remains uncovered on the wheel).

Take note of where the tire label (or other identifiable tire marking) is relative to the valve stem. Remove tube. Pump it up enough that it's firm. Submerse it in water, such as in a sink. Locate the leak. (Remember, there could be more than one; find them all.) Is the leak on the inside (the "doughnut hole" part of the tube) or the outside (where the tire contacts the tube)? If it's on the inside, then there's something about the wheel that is causing the leak. If it's on the outside, then there's something in the tire that is puncturing the tube. Since you noted the tire position relative to the valve stem prior to removing the tire from the wheel, you can isolate the two possible areas (per each leak found) of the tire (or wheel) where the debris (or wheel "defect", probably a rim strip out of place) is located. Find and remove the debris from tire, which may require pliers, tweezers, or some other tool. If the problem is with the wheel cover it by adjusting the rim strip or adding a piece of duck tape (or duct tape, if you subscribe to the alternate origin of the product :) ). Better still, replace the rim strip with proper Velox tape.

For good measure, use the cotton ball trick to check the rest of the tire. Or just use your fingers to feel for it, carefully.

Reinstall tire and tube on wheel, lining the tire label up with the valve stem (to make future problems easier to locate).

Repeat for process for other wheel.

Consider purchasing puncture resistant pneumatic tires, such as Schwalbe Marathons.

Pneumatic tires with butyl tubes have worked reliably for many decades, for millions of riders. Tubes last for many years, and a vulcanizing patch repair is reliable and permanent. It's wholly unreasonable to believe a fault in the technology is causing your problem.

Every bicycle I have ever owned from childhood until now I have had to pump the tires up to riding pressure before each ride or at least every week.

I pump up and check my tires every time I ride out of habit. I also spin the wheels to see how the bearings feel, to see how true the wheels are, and to see if the brakes are grabbing.

It takes less than 10 mins, and I know the wheels are in good shape.

Two issues.

• Typical loss of air through a tube. With a standard black butyl tube one can lose a little pressure, but it can take months for a tire to bleed down to zero. Even so, it usually has a bit of a spongy feel to the tire.
• Puncture. Can go flat from a matter of seconds to a few days. If left long enough, all air is generally lost, and there is no spungyness left with the tire/tube

All of your descriptions of your actions make it sound like you're treating it like the first condition with slow air loss.

On the other hand, your description of what is happening (losing all the air during a ride, or overnight) puts it soundly in the second condition with a puncture.

You can just swap tubes, and keep going. But I like to determine the cause of every flat.

I mark or remember where the valve is on the tire (or some people orient it with tire markings such as pressure ratings or logos). Inflate the tube to moderate pressure 2x or 3x normal size, and look/feel/listen for a puncture. If it is a slow leak, then immersing a small portion of the tube and looking for bubbles in a bucket of water can help.

Once you found the leak, compare it to the tire and rim to determine what actually caused it.

Flats can have one of a number of causes.

• Snake bite. Find mirror image two holes close to each other. Typically a pinch flat from running over some road debris with too low of pressure or too much weight. Maybe being lazy and letting tire pressure to bleed down over a month, then getting a pinch flat.
• Rim side flat. A tube if not twisted will have part facing the rim. A flat here could mean a burr from manufacturing, or bad rim tape.
• Radial Tire Wires. Look for a very thin wire sticking through the tire near where you got the flat. They can be extremely small, but sharp as needles.
• Glass can chew its way through the tire rubber and into the tube. Periodically I'll take a few minutes and pick all the glass out of my tires. But, also pay attention to flats. I am also careful with what I run over.
• Crooked Valve. Especially with Schrader tubes, the rim can cut through the valve.
• Goat heads or thorns. Problematic in some areas.
• Tire installation errors. Either snagging the tube with a tool like a screwdriver, or getting a section of the tube pinched under the bead when installing.
• Leaky valve. Rare, but also the easiest to check. Just spit on the valve and watch for bubbles.
• Blowout. Loud pop. Usually raged edge of large hole in tube. Often either a sidewall failure, loose bead, or a tube that was impinged during installation. Maybe a large hole in the tire that wasn't booted.
• Unknown. A small percent simply won't have a discernible cause. It should be the minority. If most flats fall into this category, then you aren't looking.

Finding the cause of a puncture can be a bit of a pain, but if you don't figure it out, it will keep coming back, whether it is something in the tire (radial tire wires), or something you've done (pinch flats).

Any shop that puts all the flats in the "unknown" category is doing a poor job and a disservice to you. Even if they're not patching tubes, they should figure out the causes of the flats.

I glanced through all the answers and maybe I missed it, but there is another alternative: extra thick tubes, usually known as thorn proof tubes.

I had one tire where the tire lost air over a very long period of time. I took the tube out, inflated it and dunked one section at a time under water whilst looking for bubles that'd indicate a leak. It was not until I pumped that tube up to a VERY large diameter that a bubble appeared. It took many seconds for each bubble to reappear once i wiped a bubble off. It was an almost microscopic puncture cause be an extremely fine piece of wire in the tire.

Cheers