It's so hard to put this sort of thing into perspective --- is this an inevitable problem that's eventually going to strike every Montbell UL pad owner, or a limited quality control issue that strikes just a small percentage, or ... ?
I can only say that I have over 2000 miles of backpacking with my UL 90, mostly on the PCT last year, and it's still doing fine. I'm thinking of doing the AT next year, and would definitely bring the same pad (not just the same *type* of inflatable pad, but the very same pad).
OTOH, more often than not I put a blue foam pad under this --- as a luxury, occasionally for warmth, and to reduce wear and chance of puncture on the Montbell pad. I have no idea if this helps to prevent delamanation.