How many miles can I expect to get out of my components?

[indysteel]

I know at least one of my cassettes has approximately 11k miles on it. It ended up getting swapped when I switched between a Campy triple to a Campy compact, but when I did the swap, the cassette was running just fine. I don't know that there's any hard and fast number that applies across the board to any given component; there are too many variables. So, for that reason, I approach it like Sky King. If it ain't broke, I don't generally fix it. I understand the appeal of replacing things a bit more proactively, but with twelve bikes in our stable, we replace things mostly on an as-needed basis. Plus, we don't keep track of mileage on every one of those bikes, so we can't go on just mileage.

[Melalvai]

I'm not a racer. I just commute. And go for some recreational rides.

Between the 3 of us we have 4 bikes and only 2 of them are ridden regularly. I keep my bike and my daughter's bike in good shape. Keeping track of mileage and when things are "due" to be replaced helps make components last longer-- the main thing is that if I replace the chain at regular intervals, the cassette will last 3 times as long.

I check my air pressure daily but somehow I never think to look at the tires so I'm always caught by surprise when I discover the tread is worn through. Keeping track of how many miles since I bought new tires helps me remember to check on that.