The serpentine belt on your vehicle is very important to the proper and total operation of your engine and other components.
When a serpentine belt breaks your engine will still run but your water pump will fail to operate which means that your engine will overheat if you keep driving it.
Also you'll lose power steering, your alternator will stop charging and you could do damage to your engine.
A serpentine belt that breaks on the highway will leave you stranded until you can get towed or get the serpentine belt replaced.
Always inspect your serpentine belt often and check for any cracks and if you notice cracks in the serpentine belt you really should replace it.
A serpentine belt can usually lost between 80,000 miles to 150,000 miles and sometimes longer.
But if your car has 150,000 miles on it and you never replaced the serpentine belt I would highly recommend you do so.