A serpentine belt on a vehicle should be changed every 100,000 to 150,000 miles or every 5 or 10 years depending on how much driving you do.
Serpentine belts will get old overtime and the rubber will break down and it will begin to crack so inspect the serpentine belt for cracks or possible stretching.
I usually only need to change the serpentine belt on my vehicles every 5 to 10 years or after 100,000 miles or more and I will always replace a serpentine belt on my vehicle if it's been longer than 5 years and I plan to go on a long road trip.
I hate being broken down and when a serpentine belt goes bad and breaks then you lose the power steering, water pump cooling etc.
So your engine can be damaged as a result of the serpentine belt breaking and also you'll be stranded unless someone is near to help you.
It can also be a good idea to buy a spare serpentine belt and have it with you on a long road trip or just when driving around and have the tools to change the serpentine belt.
The hardest part about changing a serpentine belt is finding out how it routes around the pulleys as sometimes that can be challenging.