I've had mine two years. Priority Eight, 8 speed with a Gates belt. The belt failed after a year, maybe 3k miles. Fortunately I was in the city, so I took transit home. Turns out the OEM belt was "for casual use", which evidently doesn't include hauling my 200 pound self to and from work daily. I replaced it with Gates' best quality belt, for about $100. The cog failed after another year, leaving me alongside the road on a cold rainy day. Gates warranted the replacement, which otherwise would have been $90. I think the replacement cog is also of higher quality than the OEM model.
I've had my share of flats. I feel like the argument about fixing flats is overstated, but has some merit. It's a bit slower, and requires belt adjustment when you get home.
Prior to the cog failure, I rode it on a Randonneuring Dart - a 12 hour ride. I'll have to be convinced the new components are much better than OEM before doing anything like that again. In 50 years of cycling, including 1200ks, 24 hour races, and year round commuting, I've never been stranded with a chain driveline failure. I HAVE snapped a chain, on a 600k, but I fixed it and finished.
I like the silence and freedom from lubrication, but I'll seriously consider switching it to chain drive before dropping $100 on another belt or cog.