Park Hopper Pluses are what works for us. For example, last November we went for 9 nights/10 days. We bought "7-day, 4 Pluses" park hoppers. (the pluses give you admission into the water parks). Here is our itinerary from November:
Day One Epcot
Day Two MGM
Day Three AK/Epcot
Day Four MK
Day Five Islands of Adventure (no Disney Parks)
Day Six Blizzard Beach (used plus only no parks)
Day Seven MK/MGM
Day Eight Downtown Disney/Resort (no Parks)
Day Nine AK/Epcot/MGM/MK (our marathon day)
Day Ten Home
Decide how many days you want to actually go into parks and choose right pass for you. We don't do PI because of kids, but you could buy admission into there. We came home with one day into parks and 3 pluses left, they never expire. So next time we will just buy a four or five day park hopper without pluses and use up what we have left from last trip.
Length of Stay passes expire when you leave and I think you can only drop one day (first or last) but I think they get you into PI. We used these once years ago, but we found is cheaper with Park Hopper Pluses.
Annual passes are good if you can get there twice in 12 months.