Check engine drive belts on a routine basis. A logical time is when you are servicing the RV or ready to take it in for service. Look specifically for small cracks, worn or frayed edges in the drive belts. While looking at the belts, check for proper tension.
I prefer to carry a replacement drive belt on my coach. I don’t want to be in a place where I cannot have a replacement available for that emergency repair. Whether I do the job or have a roadside service replace the belt, I want to make sure I have the right one installed. Some RVs have special drive belts that are not readily available and in stock. Specialty belts may have to be ordered, so plan ahead.
That said, if you plan to make the emergency or routine replacement yourself, make sure you have the necessary tools on the coach.