Did they dismount the tire and do a plug/patch the proper way?
As long as the nail/screw wasn't within an inch or so of the sidewall, plugging is totally fine and will last the rest of the life of the tire.
Check the sidewall of the tire and see if there is a ring the entire way around. If there is, I would replace. This ring happens when the tire is driven on when flat, and basically destroys the sidewall from the inside of the tire.