I've plugged a dozen or so tires in my lifetime (NYC driving leads to
a lot of flats-- lots of debris on the road). I've never had a plug
fail.

BUT-- there is the possibility, and getting another flat (or worse, a
blowout at high speed) isn't worth it. So if I had a flat now I'd
have the tire patched or simply replace it. The cost in time and risk
of a plug failing? Not worth it. Because you know that if it does
happen it's going to be during heavy rain on the way to a job
interview or first date.

-Shaun Eli
www.BrainChampagne.com