[Jeff Lee]

Adger, you missed my point that if a visual inspection revealed a problem, even sun discoloration, then they need to be replaced.
That could mean replacing every race if there is something wrong!
A brand new set of belts, if improperly installed, will not be fully functional and are subject to failure.
A set of belts that look as good as new, are as good as new in my opinion.
Anything less, needs a replacement set.

I may be wrong but I think belts for fighter planes and sprint cars are not replaced on a calendar, only on poor quality.