I carry the
Safety Seal kit in the truck, I can make tire repairs from FOD on the road. Never had a problem with a plug either leaking or failing. I'm talking about your average nail/screw puncture, not major damage, and only in the tread area.
If you plug the tire correctly and if you are using a quality kit, it will provide a safe reliable repair for the life of the tire. Two big IFs in that previous sentence.
In fact there was only one time I recall on the road when I wasn't able to successfully repair a tire with a plug, I just couldn't seem to get the plug to hold:
