Everything I read says that if you buy LT tires, they should be replaced in 5 years. If you buy dedicated MH tires (we just bought Firestone MHT's - stuck with 16.5 rims) then the recommendation is 7 years. Mind you that the tires which came off have a date code of 1993 and still survived the 30 mile trip home (at 60 MPH) when we purchased it. A good friend bought a great condition class C and has had three of his tires burst. Expensive on-road repair for that, so I say change out the tires and go 7 years max.
Jose
