We bought into
DVC in 2003 and have been very happy with our membership. I was reluctant in the beginning, it was my wife who wanted to join. We were getting ready to have a family, and we both had a love for Disney, so she eventually brok me down. To this point - I have no regrets.
But, it sounds like you have very specific ideas about your membership.
#1 - If you want to stay in the EPCOT resorts, I suggest you buy resale into either Boardwalk or Beach Club. We were able to book the Boardwalk in 2006, but on subsequent visits, there has not been availability for what we are looking for
#2 - We are planners, so using the 11/7 month window is not a big deal for us. We did book one vacation on short notice in February 2008, we were able to get a 1 bedroom at OKW, not sure about other resorts and availability. I know that Boardwalk and Beach Club are very difficult to get in the fall due to the Food & Wine Festival, so I dont think it is limited to the month of December.
Again - I am of the mindset that we are staying in Deluxe accomodations on site. I have favorite resorts, but dont mind where we stay, so I dont get disappointed. I love being at Disney, and the comfort of a 1 or 2 Bedroom makes our stay that much more enjoyable.
I dont blame you for rethinking your purchase, dont settle for less than what you want.
Good Luck