Well, I had a flat in my thorn-resistant tube last week, and luckily I had a spare tube to replace it. I just patched the thicker tube. Looking at the weather for the next week and not seeing a single overnight temperature above freezing anymore, I decided that I should be wary of morning frost, which is mostly what caused my falls last year.
I put last year's screws into the tire and remounted it with TWO split junk tubes as liners over an already thick-walled inner tube. If that isn't enough to prevent a flat tire from the screw heads I don't know what is.
I just wish that I had water-bathed the patch to be absolutely sure of its integrity....