I looked into this when we bought our Beyond with the belt and the responses were 10K to 20K miles before replacement is needed. At 6K miles we started to carry one in the travel case just as insurance that a vacation doesn't get ruined. I guess I worry more that I may kick something up that could cut the belt, but those things are pretty tough so I don't really see that happening. If it did break I would probably move back to the stokers seat and I would guess we could make it back to the car or at least civilization where we could get a ride.