You need to book at 11 months out for early December, Christmas and New Years. From mid-Sept (start of Food & Wine) through mid-Jan it can be hard to get something DVC at seven months out. You might find SSR, OKW or AKV, but not the villas that require the fewest points (studios). And trying for a full week can be hard at seven months out.
DVC members tend to stay for running events (marathons, half marathons, ten milers, etc), holidays, Disney events (F&W, F&G). Summer gets spread out over three months, so it can be easier to book at seven months out.
But if you constantly need to book at three or fewer months out, you might be disappointed frequently.
BCV, BWV and BLT tend to be favored. Also the new GFV (it's the smallest of all other than GCV). Value villas at AKV, standard villas at BWV, any villa at BCV, standard villas at BLT are all popular. BWV only has seven GV so they go fast. OKW has more GV, but they require the fewest number of points, so they can go fast. VWL studios may become the new hot ticket since they sleep five and are very limited in number (it's also a small resort).