I don't think pre-glued patches should be used. There are concerns on whether they are as permanent repair as ordinary patches.
If you do patching properly, it's a permanent repair, and the tube becomes as good as new. What you do is to first remove the mold release using sandpaper, then apply a thin layer of glue with your finger (no, you won't get a cancer from that), wait for it to slightly dry (you will see it visually), apply the traditional type patch, create a slight slit in the middle of the plastic cover with a razor blade, stretch it along with the tube so the new slit becomes larger, and peel the just halved plastic cover away from the middle so it won't lift your patch, and NOT USE THE PATCHED TUBE YET. Yes, that's right, a recently patched tube should not be used for a day, because it takes a day for the glue to fully dry.
So if you can't use the patched tube immediately, you need a spare tube (and the recently patched tube becomes your new spare tube). Usually one is enough. In absolute worst possible case you get multiple punctures in the same day, and if that happens, then you obviously have to use a recently patched tube, but that's so rare that it's probably better to just use recently patched tubes and treat them as possible loss than to start carrying N spare tubes -- which wouldn't help in any case since you can get N+1 punctures.
Theoretically you could delay patching the tube so that you can start riding your bike faster, patching later at home, but then you may get a second puncture, run out of spare tubes, and need a recently patched tube as a spare. It's better to use a tube patched 30 minutes ago than a tube patched 1 minute ago. Also, patching is very fast so better to patch right away.