about 235 days of bike commuting, 30 mi/day, ~7100 miles total for the year. That is about 470 hours on the bike. I ride a 55 lb, 28 year old, $500 mtn bike with panniers...
I had to drive my car to work 2 days this year due to required long side trips.
4 new chains, 1 new bottom bracket, a new freewheel and large chain ring, no flats or other mechanicals while riding... no complaints except the daily need to clean the bike of mud, crud, sand, and dirt...