I just replaced my Pro Ones (32mm). The rear took a cut from a thorn that was about 1/8” (3mm). The cut sealed itself and lasted for several rides, but it was losing more air over night than normal so I patched it on the inside. It lasted about 2 miles at 60 PSI. Bulged up really badly and that was that. They sealed any number of punctures over about 3000 miles. The tiny cut, not so much. Maybe with fewer miles it would have been a different story.
Replaced with another set of Pro Ones.