The funny thing, with all this talk of interior patches and other more difficult methods, is that I've yet to install a simple gummy worm plug, that didn't also outlast the tire.
That said, I won't even try installing in sidewall, which is just asking for a failure. I also won't count on one right at the shoulder of the tread being a long-term fix, they're just not designed for that.
But anywhere in the tread, other than the outermost 0.5 inch, every last one I've ever installed has outlasted the tire. In fact, even the one I did install right at the edge of the tread held just fine. But I'll admit I only kept those tires on the car a week or two past plugging, as they were cooked anyway.