How long do inner tubes last? I recently started biking again after taking about 2.5 years off. My bike has been sitting in my garage since then. I did a 30 mile ride as my first one back and I didn't replace my tubes beforehand. Everything went surprisingly fine, but the whole time I was worried about getting a flat. I did have a spare with me, but it's as old as my other tubes.

That got me thinking, how long do tubes usually last while they are in storage, both on and off the bike? Do I have to worry about dry rotting/cracking?
Generally speaking, 


  Inner tubes will last forever, until you get a flat


Unless the tubes are very old - I'm talking 15+ years - you don't have to worry about them dry rotting, cracking, or loosing structural integrity. I have a collection of patched and new inner tubes from since I started riding around 9 years ago, and all of them look brand new.

And in my experience, the most common cause of flats is due to me doing a shoddy job of installing the tube (ie, the tube is pinched, stress on stem, etc). Back when I started working on bikes, I would regularly get flats a couple days after installing new tubes.

In short, if the tubes have lasted this long, and still hold air, don't touch them. I even remember reading (on Sheldon Brown's website?) that he has witnessed very old tubes bond to the tire.