I use the pre-glued patches and have several tubes with multiple fixes on them.

They have failed exactly three times.
Twice when I didn't let them sit overnight, under pressure, (I usually apply the patch and then put that part of the tube under a heavy book, for the night).
And once when the puncture was on the side of the tube.

My conclusions from this are that if you want to patch the side of the tube, use the ones requiring glue.

One last point here, don't let anyone tell you that patching, in general is ineffective. Every tube in use has been patched. How do you think they get the stems onto the tubes?