GD's waiting period is now down to just a year or two, but the big thing is getting enough panelists to the course to qualify. I believe it takes 45 panelist visits to qualify for the Top 100 list, 25 panelist visits for the Top 100 Public list, and 10 panelist visits for the Best in State Rankings. Those visits are accumulated during an eight year period. Therefore, for this newest survey, ratings turned in by panelists during 2009 and 2010 replace the ratings from panelists entered during the 2001 and 2002 survey period. That transition each survey can account for a certain amount of movement depending on conditioning standards, remodels, changes in the rating criteria, etc.
While the rankings will always have surprises to people and their personal preferences, taking the average of 45 (minimum) panelist opinions is a pretty healthy average to take. If you look at the history of the Top 100 vs the Top 100 Public list, the Public list has a lot more movement and inconsistency due to the averages being taken from a smaller sample size. There may be a lot of GD panelists, but I do think it is beneficial that they pull their data from a larger sample size.