Having PPF for over 2 years now. These are the panels I would consider "important".
Rear bumper: I have just the part behind my wheels done, I would do it again I'd ask them to make a bigger film for that area. (not the whole bumper)
Mirrors get a beating, (I have them done) but at the rate they charge you for it, you can respray them easily.
Final thought: the film protects your car and paintjob, but don't expect it to hold off everything.