it's the owner, terrain, and weather that's more important.

I rode 3500 miles on my bike this year, and my bike is pretty much indistinguishable from the day I got it - except for the brake pads and tires. i replaced the chain at 3000, noticed an improvement. I keep it clean, and periodically disassemble things to clean and re-grease them.

i'm actually selling my bike now, and as far as i'm concerned the mileage has not depreciated it significantly.