I had some difficult math this time around.
My family of 4 last went for a big trip in 2015. We were planning to go in summer 2018 (12 days) and summer 2019 (10 days), with a food and wine trip in October 2018 (4 days) .... but then the opportunity to finally go at Christmas came up and we took it. I had to build a whole spreadsheet to justify value, but basically it came out to making sense to get 1 Annual Pass this trip (for discounts and Tables in Wonderland), and then get 3 more Annual Passes next July for the rest of them. I'll then have to do the math in 2019 and decide if cheaper to renew my Annual Pass or just buy a "per day" ticket.
The general rule used to be if you go 10 days in a calendar year, or if you stay off property and go 7, it made sense. It's a little tougher to do the math now.
The only thing that bugs me (that they still haven't figured out) is how to get you your customized AP Magic Band before your trip. Last time we had to buy 4 of them when we got down there, because we were staying off property and they wouldn't send you Magic Bands until you activated your AP - and they had no way to just give you some when you arrive. Very frustrating. Luckily not a big deal for us anymore as, like most people, we now have a garbage bag full of them.