We can fix or answer ANY question here at AnandTech. *big fat grin*
That all depends on your make, model, and engine. Most timing belts need to be replaced between 60,000 and 75,000 miles, while others are typically good for 90,000 miles. To be safe, you should replace your timing belt every 60,000 to 75,000 miles reguardless, unless your manufacturer recommends more frequent replacement.
This topic should be covered in the "scheduled maintenance" or "repairs" section of your owner's manual. If you don't have one, I'd suggest a trip to your local library, to get a copy of the Chilton's manual for your car, which will tell you how often you should replace your timing belt.
Gods I hope the mods don't lock this thread.. it -is- technical support, of a sort.

J/K, but serious about the answers.
