i think the op opinion is a good one, and so is dans, a little overboard but still he has a point.
the WHOLE IDEA is to take good care are of your tires. with major rough use of your tires, five years may not be too soon to do a replacement, and 10 years for a gently used set of tires.
arbitrary replacement on a time frame would be ok if money is no object. most people replace their tires because there is an appearance issue, i.e. cracks, cuts, wear patterns and of course age.
a good visual inspection of the sidewalls, and the tread should be done every time you use your coach. tire pressure should be done every week, while on the road, sooner, if the roads are rough. a thump test every morning as part of the departure inspection.
checking tires is just as important as checking the oil, or any of the other dozen things you have on your departure list, and is commonly ignored.
i have only had two blowouts on motor homes in over 45 years of driving, and i can tell you,blowouts are not fun. they are one of the most puckering experiences ive ever experienced. both were caused by sidewall failures. apparently curb bruises.so now i apply an ounce of prevention.