There appears to be a lot of high quality belt drive units out there and can't imagine that the typical "old" bike owner is going to be putting so many miles on his bike as well as one that has so much torque that he should be worrying about snapping his primary drive belt.
If that were true then Bob Newby would have been out of business with his racing clutch and belt drives years ago. I've been doing my level best to snap mine for the last two years and 5000 miles and so far the teeth still look brand new and the belt is only 1" wide. Tyres are another matter as I've already destroyed two Avon Roadmaster rears in that time and mileage and just started on the third one so there's no lack of torque there.
The things I like about the belt drive are: It's quieter, requires no adjustment in service, runs clean and dry so no chance of an oil leak, I can run a sweet dry clutch and the belt makes the transmission smoother and less snatchy.
Another thing about people breaking belts is a belt requires about an inch of up and down play cold to allow for case and drive drum expansion when hot. This appears excessive to the uninitiated and they set them too tight and then wonder why they snap at some point.