A car's timing belt should be replaced every 50,000 to 100,000 miles, depending on the manufacturer. A car's serpentine belt, which drives its accessories, can last as many as 150,000 miles. Many pickup trucks and some sedans use timing belts made of metal, and they do not need regular replacement.
The timing belt has to be replaced more frequently because it undergoes greater loads than the serpentine belt. When a timing belts fails, the engine stops, and it may suffer damage because the belt no longer regulated the firing of the pistons. The serpentine belt breaking also causes the engine to stop functioning because many cars use it to power the car's alternator.