DVC resorts, and the program itself, are designed for the resorts to be near capacity at all times. It is really the only way a flexible point based system, rather than an old style set week timeshare, can work. Otherwise you'd end up with a lot of unused points every year.
If DVC notices a particularly slow season or an overly busy season for booking (not counting major holidays, obviously) they will adjust the
points charts to compensate by making some seasons more expensive and other seasons less expensive. This has happened once, in 1996, at OKW. They still have to work within a given framework as each resort has a set numbe of points for use annually.
That being said, September and mid January (except for MLK weekend) are probably the slowest DVC demand timeframes. BCV & BWV also book up quickly for the EPCOT Food & Wine fest, and f course, Spring Break, Easter, Thanksgiving, Christmas & New Year's are all peak times. Early December is also very popular, as the points are in low cost Adventure Season and the parks are in full Holiday mode.