Yes, they may come off or move around. It is best to remove oils from your skin before applying. Dry the area carefully with a low setting on your hair dryer too.

Sometimes you can activate the glue with a puff of steam (like from a tea kettle). The adhesive is water reactive. It swells up when exposed to water. Take one that is to be discarded and expose it to moisture like in a shower--indirect moisture. It will jelly up in a very alien strange way! Keep away from animals (and children), as they may be attracted to the adhesive, and try to eat the old patches. I fold and stick them to themselves, and put in their old envelope and fold that down before tossing in the trash.
Too much and it slides around. The sliding often comes from skin that sweats too much. If they do not feel COLD when you apply them, they may be drying out.