The original Ohtsu tires on my 1982 200 were getting a bit dry rotted but were functioning fine. Yesterday, one of the back tires was flat with a hole in the sidewall. When I went to plug the tire, it tore on the crack line, disintegrated and the then tread separated from the sidewall. So if my ATC was made in 1981, that puts the tires at 28 years old--not a bad run at all I would say. Honda did build these things to last-right down to the tires.
I have some Cheng Shin's on the way and new O rings for the split rims so hopefully those will last the next 30 years.