If I only wanted studios at VGF, I would buy the fixed week option, assuming availability for the week I wanted. IMO, that's the only way to go, especially if one prefers to travel during the last 3 months of the year. (This may end up the best strategy for the Poly, too, but IMO, it's too soon to make a determination there).
Johnny D, I think you have been lucky and that your experience is not typical. There are too many reports of others ending up disappointed to suggest otherwise.