Actually the summer months when the rest of WDW is busy are relatively quieter for DVC. Folks who have a choice usually don't want to deal with the heat and crowds. Note I said "quieter" not slow. I wouldn't wait 60 days out and then wonder why I couldn't get what I wanted.
Also reasonably slower is January, once you get past the Marathon. the Feb/March/April time will vary depending on Easter/spring break timing.
Late August/early September is pretty slow for DVC.
Any date from October 1st through the Christmas holidays is going to get more challenging for DVC reservations. 11 month day by day is not necessary (unless you want Christmas week in a GV) but I wouldn't dawdle about getting a ressie made in the 10th or 11th month out.
In addition, reservations will always be more difficult at "the littles" - BWV, VWL and BCV. They are just smaller so they fill up fast. Studios go quickly.
There are exceptions to everything and someone will jump on here and say they got BCV in December at 4 months out, but they are probably exceptions. If you are particular about dates, resort and room size you need to book earlier during the busy times. If you are a bit more flexible, you have more wiggle room.