we buy these belts because they supposedly are SAFER than OEM belts, yet 50-60 year old belts are ok, never mind the possibility of them being "stored" out beside the shed for the last 10 years or so. if they are so good at that age, why even bother to install aftermarket belts that need to conform to xyz specs ? just head out to the local junkyard and grab whatever belts you can find. they will be FINE !
and as to the "slower" cars not needing aftermarket belt replacement every two years, not around here. you put those belts in, they need replaced, period !
unless, of course, you run at an outlaw track where almost anything goes.
the excuse given for the two year replacement rule is "we don't know what condition the belt is in." well open your eyes and look ! frayed stitching or webbing, hacks or cuts, improper mounting ? good cause for rejection. yet dried out, stiff webbing, frayed stitching, rusty hardware factory belts still ok ? yeah, RIGHT !