I had to use a plug recently and it got me home from out in the middle of nowhere. My tire was flat a week later when I went out to check it. I don't think I used enough glue. I keep the kit with me all the time.
I found these tire tips from Dunlop TIPS
. They say max speed after a repair should be 75 with a plug patch.
The subject of Tire Patches is probably as touchey as OIL. I probably had a thousand miles left on my Tourance when I plugged it but I replaced it anyway. I figure a new Tourance is $100, medical expenses can add up quickly so I go conservative.