Originally Posted by
paulb_in_bkln
I think "indefinitely" is the right word. Barring an accident. Neglect can ruin them--I see abandoned Raleighs here all the time where the frame, fenders, rims, and BB are beyond recovery--but with maintenance the bike, not counting chain, cables, brake pads, etc., will go forever.
I agree, completely! The failure modes of steel parts (including tubing) are well-known, and steel parts don't just break if they haven't been under excessive (i.e. inelastic) stress.
Prevent corrosion, wear, and undue cold-setting, and there's really no reason the steel parts of a 3-speed should fail. Rubber parts are maintenance items - use them as long as you can, but just being in atmosphere they will degrade. I realize this can re-open an old argument about fatigue of steel, but, well, I'm not going to argue over long-established science. Use the Wiki.
I really don't have concerns about using 10 year old tires with no signs of decay, but ... not 30 years or more.