At this point, I don't think that you could ever count on your vacation costing the same amount of points from year to year, even if you are traveling at the same time of year in the same accommodations.
We purchased at SSR in November of 2004, with the minimum investment of 150 points, and for our last 2 trips in June 2011 and scheduled for June 2013, we have had to make adjustments to our accommodations due to the reallocation of points.
My husband is a teacher, so we can only travel mid June through mid August, which does limit our flexibility. When traveling in June from 2005 to 2007, we always had a studio at SSR, and it was plenty of room for 2. We used points Sunday through Thursday, paid cash for Friday and Saturday, and used points Sunday through Thursday the next week for a total of 12 nights. We did notice that Friday and Saturday nights, the parking lots were practically empty, so there were a lot of people maximizing their points and checking out on the weekends. We still had enough points left over for 2 short 5 day trips in January 2006, and January 2008. (hubby stayed home) Our daughter was born in July of 2008, so we banked our points and used them in June 2009. We stayed in a one bedroom villa at SSR for a total of 12 nights, while using points Sunday to Thursday nights and paying cash for Friday and Saturday in between the weeks. Our son was born December of 2009, so no trip was taken in 2010 and our points were banked. We were planning our trip for June 2011, and wanted to stay in a one bedroom villa at SSR for 12 nights, paying for the weekend, just as we had done in 2009, but because they reallocated more points to the weekdays, we didn't have enough points to do the same thing we had done in June 2009. If we wanted the same scenario, we would have to pay cash for 3 nights now instead of 2. We decided to only stay a total of 11 nights at SSR, and 2 nights at the Royal Pacific Resort at Universal. We would get a studio at SSR for the first 5 nights, and a Treehouse Villa for the next 6 nights. The move wasn't bad, the Treehouse Villa was awesome, so we decided on our drive back home, that we would do the same thing in June 2013. NOT SO FAST.....
They took points from the 2 bedroom villas at SSR in the offseason, when we can't travel, and added them to the Treehouse Villas, essentially taking away one of the nights that we were going to stay in the treehouse in June 2013.
I realize that the reallocating of points may have helped a lot of people, but it really hurt those that cannot be flexible with times they can travel. So I would caution the OP to purchase ENOUGH POINTS so that they can roll with the point reallocations, and not panic every time the new points calendar comes out as we do.
We made our reservations for June 2013 this morning. We are only staying 10 nights at Disney. 5 in a studio at SSR and 5 at THV. We are now going to stay an extra night at Royal Pacific Resort at Universal, for a total of 3 nights.
I am very fortunate enough to have the means to travel to Disney, and to be a
DVC owner. I don't mean to sound ungrateful by any means, and I know that we do stay for a long time. I will eventually buy a large add on to SSR, which is what Disney wants me to do in the first place, but I think I will wait until they decide to move the month of June to the premiere season! With our luck, they probably will!
Bill
) then we will have some extra points to play with. 
