You get different answers from different people at Marriott when you ask this question. Easiest way for me to handle it is when they offer points, I take the tour. Once they called back and said that I had already gotten 15K miles from a tour of another facility, and they could not offer it twice in a year (or maybe again in 6 months), but I just told her, thanks but no thanks. Once you get there and take the tour and have the piece of paper stating you get points, you're pretty much golden. One time I had to call back to get it to post, but most times it posts automatically.
To me, the value of the points is nearly $300, so I'm glad to donate an hour or so to look at a property I might exchange into someday.
I think it helps that I already own three weeks at two different resorts.
Billy