Originally Posted by Seattle Forrest

Basically, take your budget, double it, and lust.

Every part of a bike will eventually wear out, given enough use. Even the frame. But it'll take a long time, so much that it doesn't make sense to worry about.

At 4,000 miles per year, your foremost expense will be tires. How much you'll spend and how often you replace them will depend on which ones you use.

New brake pads are less than $10, and it's easy to put them on yourself. The wheels should last you years, if you ride don't them down stairs and over potholes and whatever else. That covers the rim (which wears down slowly as you use the brakes, and also can get bent in a serious impact like hitting a big pothole at high speed), axles, and the whole nine yards.

You'll need a new chain somewhere in the ballpark of every 1,500 to 3,500 miles. It'll cost between $20 and $75 depending on which one and where you buy it. You'll need to replace your cassette (gears in the back) every 4 or 5 chains. You'll need to replace your chain rings (gears in the front) after maybe 35,000 miles. But this stuff lasts longer if you don't ride in the rain, and if you lubricate the chain when you should, and all that great stuff.