After having tire issues on our one Camper I replace them every 5 years even if they look good. One guy who is a mechanic at the RV place who inspects them told me 4 years would be better as he is seeing them come apart/bubble in 4 years. Tires just are not what they once were.Most made these days are junk, like what has already been posted. Working at an RV dealer, I see good and bad. So with that being said I will tell you what I have personnel experience with on my car trailer and my two boat trailers. I use Hercules brand trailer tires. Also Goodyear Endurance tires (not Marathons). The tires should be good for 6-8 years as long as they are taken care of and not neglected. Keep them aired up, keep them covered, its important to take care of them.