Like Tara, I had heard that an owner could not have more than 5,000 points. I had also heard that an owner could not have more than 2,000 points at any single resort. However, when we were at WDW in March, one of the Guides mentioned that they increased the resort limit from 2,000 to 3,000 or 4,000 points. Frankly, I'm not too concerned about any cap limits on the number of points I can own. Its like special tax laws that apply to billionaires: I'll worry about it when I get to that level.
BTW: A few months ago someone started a thread in which he said he was planning on staying nine months at WDW. I don't know what became of his plans.