It really depends on the time of year, what kind of room category, how far in advance you get on the list, etc. We waitlisted a week at BWVs one time for a stay in August. We had been on the list for about 6 months and it finally came through about 1 month before our trip.
On the other hand, when we went last October we had 5 DVC resorts waitlisted and NONE of them came through.
I can't figure out any rhyme or reason, sometimes just the luck of the draw.
Good luck!