I've got 54,650 miles on a SRAM Rival 53/39 crankset with original rings. Shifts fine without any unusual noises or catching. No need to change.

I think riding style (not shifting under load, spinning etc) and keeping the drive train clean are the real determinants of longevity - not number of miles. Last week I just installed my 4th cassette and chain - yes I replace them both at the same time. I've averaged about 18,000 miles per cassette/chain.

I live in North Texas and ride all year long.....I'm retired and try to ride every day.