my 06 Ully is still on the original belt, 37k and 14 years old, my old 95 Harley road king was still running its stock belt when i sold it 5 years ago after 40k and 30 years, if taken care of they last a long time!
I have also been told that whenever you replace a belt your front and rear pulleys should also be changed out for new, not sure if thats the same on a buell as it is a harley but worth thinking about..
My 2000 fxdx had 140,000 miles on it with the original belt when I sold it 3 years ago. The belt looked fine to me when I was washing it for pictures and delivery. Even the pulleys looked ok. It was a 1-1/4" vs 1" but the engine was hopped up quite a bit although these belts can handle a lot more than what most reasonable people would put through it. Even the pulleys looked fine. But just because my peak HP was 150% of stock doesn't mean I ever rode there consistently, so I was within design parameters 99% of the time.
It's kind of why I offered up the question. The HD is gone but the Buell will age more than I will add to the odometer as I plan on my X1 remaining a "forever" bike so it will remain a fair weather ride only. The 2 belts I have hanging up, I'd like to last. I guess I could vacu-pak them and put them somewhere dark and cool. I did that with my spare isolators. Like a squirrel with nuts, I just gotta not forget where I put them.