I'd also wait to buy until just before your trip.
Some people bought Power Passes (PPs) and then USF decided to change the black out dates. They didn't do this early in the year, oh no, they waiting until a few weeks ago to spring that one. Some people complained and were grandfathered in, but others are out of luck.
Plus, most AP deals happen early in the year, as the parks try to get everyone to buy tickets during the off season. Check in Jan or Feb and make a decision then.