Patches will gradually come off too. The bond deteriorates with just plain vulcanizing rubber cement when the tire flexes, even with lots of surface area to spread the bond strength out. Brand name stuff like Rema Tip top also failed to be permanent. They will get you back to civilization though. I've gone as far as using clear RTV as an at-home permanent repair, to try saving a relatively new tire, but it wasn't good enough either. Ended up deforming the tire since it wasn't flexible enough (that or I sanded a bit too much).
The plug fell out the hole on the first full speed right hander I made on pavement (leaning with speed/Gs). It held on the trail though. I just got a bit too confident in it holding and found its limit. Muc-off sealant didn't cover for the patch failure nor act as adhesive (quite the opposite).
Patch was fine over night, but I ended up pumping up the tire after 45 minutes of riding, then 30 minutes, then 20, to compensate for slow air loss as the patch gradually failed, until ride buddies were showing concern with the tire, wanting a more permanent fix.
Repairs not holding, and the ride quality suffering slightly (felt like riding over large sidewalk crack with every revolution), just encouraged me to just get a tougher tire to avoid failure in the first place. Cush Core didn't make up for running a flimsy tire. Running new super gravity tire without cushcore successfully so far. Tried double down and that felt pretty solid too (actually held air well enough to do a 1-2 hr ride without sealant), but overcompensating with SG for now.