Our family have three bikes with belts and Rohloff. One thing I have learned is to ensure the tension is correct. If not sure, keep it on the looser side. I had a belt that was definitely too tight and the belt wore very quickly to the point the belt was losing teeth. Once I adjusted the tension using the Belts app, the wear stopped but I soon replaced the belt due to the missing teeth. I figure that was just an expensive learning lesson.
As far as touring with a spare or not, I always have a box at home (or a with a friend) so that that my lovely bride can fed-ex the belt (or various other parts I really don't want to carry) to me should I need them. For me, I am not too worried if I have to hole up for a few days. However, when I do some really remote touring at times where the chance of coming across somebody to hitch a ride back to a Fed-Ex-able town, I do carry a spare using the triple look method. I put it in a zip lock bag and put that in an old stuff sack and put that in the "sleeve pocket" (not the zippered pocket) on my Ortlieb that is between the inside "wall" next to the tire and the zippered pocket on the inside of the pack. No issues so far.
In summary, ensure the belt is properly tensioned and you are probably good to go.
Tailwinds, John