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Silent,

I don't think anyone would argue that it is bad to use D range tires when C range would meet the load requirements. There is nothing wrong with wearing a belt and suspenders if that is a preference.

I will disagree with you over the tire replacement for age issue. As you own and operate a trucking company I doubt very mush if you have a lot of experience with your tires reaching five or six years of age before the penny test fails. So, I guess your opinion is probably based on tires used for vehicles or small craft trailers.

My experience of using tires older than six years is fairly extensive. I've been retired since 1996, have a car, a pickup, and two boat trailers. The pickup is a year old and has a whopping 4000 miles of use. The car is six years old and has 14000 miles on it. My main launch ramp is less than a mile from home so my trailers are very low mileage. So I have about fifteen years of experience with tires that age out rather than wear out.

Tires are cheap. Cars, trucks, boats, trailers medical expenses and funerals are not. Consequently I follow DOT and tire manufacturers recommendations on tire replacement intervals for age. Is the penny test not a DOT and tire manufacturer recommendation?

I say let your judgement be your guide but I do try to pass on information that is known to me to be endorsed by more than just my experience. I won't express an opinion known to me to be contrary to widely followed government and industry guidelines. I would hate to cause harm to someone for following a suggestion I made.