Age of tires on your tow vehicle/ When to replace?

If you are not traveling enough to wear the tires out then age is the determining factor. Most of what I have read on this forum suggests five years max. I replaced what I thought to be perfectly good U.S. made Marathons because they were five years old, I only had 6300 miles on them but I know for a fact they were run above the recommended 65 mph on several occasions on some of the hottest days of the year. This was before I learned about max speeds on trailer tires. I would rather spend the extra money changing tires before they really need to be rather than risk a blow out that can do considerable damage to the rig and possibly even cause an accident.

Not everyone can afford to change tires just because they are five years old. Everyone's situation is different and you, the OP, have to make your own decisions based on your cash position and the level of risk you are willing to take.