Peter, correct me if I am wrong but I think the five year time will limit you on the Michelin or Chinese tire. We all face the same problem with getting to the time out before the wear out period. I feel that after five years you are traveling on borrowed time that could cost a lot more than just a new tire.
I installed Goodyear RV tires on my 99 Marathon, 315R80-22.5 and although I needed some help due to irregular wear, Goodyear stepped up and gave me 4 new tires for the labor only after 32000 miles. I will keep using them as long as they will keep changing them FOC due to a funny wear pattern.
Kevin