If the tire plug was properly installed then it should last as long as the tire lasts just like a regular tire patch.
I've had a tire plugged and since it was done properly it lasted 7 years before I replaced the whole tire due to wear and age of the tire.
So if you plug the tire it should last just as long as a tire patch although getting your tires patched is much better but a tire patch can be okay and just as safe if installed properly.