My boys and hubby travel less often to WDW than I do, so we always get them 7-Day PHP tickets, and use as necessary. I tend to keep an Annual Pass and and PI Annual Pass.
We always have plusses left over. I try to keep as many tickets with at least one plus on them as possible, instead of using up each ticket one at a time. That way when friends join me at PI or a water park on my solo trips, I can hand them a ticket with a plus on it.
It makes it a little more difficult to keep up with, but at the beginning of each of my trips, I just go to a window and hand them each of my tickets and find out what's left. I then ditch the empty ones.
Carol