LOL, my DW was making fun of me for the spreadsheet I was making when I was initially buying into
DVC. Sure, you can crunch the numbers and optimize the math. But for something that you're planning to be stuck with for many years & decades, choose wisely.
Sure, for the price, the money is an important part of the equation, but it shouldn't be the only thing. There are several resorts, themes, locations, amenities, transportation options, dining options, etc. Buy somewhere that you can book in the 11 month window and be happy with just in case you can't change it during the 7 month window.