Probably between 18 inches and 3 foot. The ultremos were shot to pieces quickly, certainly inside 500 miles. The gatorskin i bet hadn't done 200 miles from new. Owner of the local bike shop said he hadn't seen that before. I'm putting it down to bad luck.
I sold some ultremos beforei ever used them as i heard although they are the bees knees for riding they cut up terribly.
having used gaors for years i cant say i have ever only had 1 sidewall go , the normal maintenence routine of checking for debirs in any small cuts and supergluing the hole is all i have had to do to keep them going.
At a loss tbh, without seeing your bike and route its hard to say.
On the commuter i am currently using lugano`s blizzard sports as a cheap alternative and they have been ok for a cheap tyre, maybe a little slower than better tyres but ok for general riding and i have used them on club runs and not felt to disavantaged.