I have had two tires plugged, and they worked just fine.
On a national holiday, I detected a screw in my front tire,
while touring Newfoundland. I sought assistance and got lucky.
A fellow led me to a group of people working on vehicles of all sorts,
and half a dozen guys volunteered to plug my tire. One of them won.
The only difficulty was persuading my benefactor to accept a tip.
I prevailed by pretending I was superstitious and wouldn't trust the
fix unless I compensated the fixer. That tire carried me several thousand
miles before it was discarded.
A couple of years later, I found my own nail, and plugged the tire myself.
Again the fix lasted as long as the tire. I never gave it a thought.
I understand that if a plug fails, the leak is generally slow, and you
can often try again with more glue or a bigger plug or both.
Your Mileage May Vary, as we say in these situations,
but I have learned to be confident of my next plug.