I go at least twice a year - 7 nights both trips. Where I stay isn't overly important to me, as long as it's on Disney property. We figured, well, we have annual passes already, so that's out of the way. And with AP discounts, you can stay at a Value resort for about $50 a night or a moderate resort for about 80 a night.
So, we basically averaged about $1,200 a year for accomidations which gave us 2 weeks.
One thing I was SHOCKED to find out - When you're a DVC member staying at one of the resorts, you don't get room service. You don't get more towels, unless you buy them. May sound like a silly thing, but it certainly doesn't help sweeten the deal.