How long does a tire patched with the plug method last?

The deciding factor is where the puncture is located: if it's on the sidewall, the patch won't hold as well as on the tread, because the tire flexes too much while driving. On the tread though, if the repair is done properly with the right glue and you press it down well, you can easily get 2-3 years or even more out of it, depending on how you drive and how fast you go. The important thing is to check it every now and then and not trust it 100% like it's a brand new tire, especially if you're planning long trips.

With a plug repair rather than counting on 1-2 years, it really depends on how much stress the tire is under - if the puncture is on the sidewall or in a high-flex area, even a well-done repair will hold up less, maybe just a few months. If it's on the tread or in a more stable part of the tire though, you can get longer life out of it, but it's still always a temporary patch and not a permanent solution for long-term safety.

A strip rubber patch, if applied properly, can easily last several years, not just 1-2 like some people claim. It really depends much more on how the tire gets stressed than on the repair itself.

What matters is the context: if the puncture is on the tread and you drive normally, the patch holds up really well. I once repaired a tire that way during a trip in Nevada and used it for another two years without any issues. The critical point is when the puncture is on the sidewall - there the tire flexes constantly while driving and the patch tends to lift at the edges. Same thing if you have a hole near the tire shoulder. In those cases, yeah, the lifespan drops noticeably and you risk the repair not keeping up with the stress.

The quality of the patch and how you apply it matters a lot: if you clean it poorly, if you don't roll it down properly or you use a cheap product, the lifespan tanks. But done decently on a "low-stress" area of the tire, that strip patch can stick with you for 3-4 years easily. It's not a permanent solution in the sense that you'll eventually replace the tire anyway, but as a temporary fix it does its job.

Have you ever noticed that how long it lasts also depends on how clean the surface is before you apply the patch? If the rubber isn't properly degreased and prepped, the adhesive won't stick the way it should and the repair can fail way sooner. Beyond the hole area and the driving stresses that others have already mentioned, this is the detail that often makes the difference between a patch that holds for decent years and one that pops off after a few months.