You need to check your owners manual in the maintenance section to find out the recommended mileage. If you have 100,000 mile and it says to replace it before then, you're driving on borrowed time, make sure you do it soon.
If the belt breaks it can cause damage to the engine and cost you a lot of money to repair. You should also check into doing your water pump at the same time while they're in there. No more labor, only parts cost.
In March AskPatty will be adding a feature called MyCarPage, there you can register and get automatic email service reminders based on your vehicle make, model and year, exactly as your manual recommends from the manaufacture. Check back mid March for this great new feature.
〉 Answered on Mar 2nd, 2007 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines