Chris, they can turn over more than twice a day - a quick look at the RG Results page shows you - and bhoese is right with the 50C KI RG - it's filled out around 17 times in the past 3 days alone.
http://www.wgt.com/tournaments/readygo_old.aspx
After an RG is filled it restarts on the game page, but not for those who entered the original filled RG - they have to wait unit the original RG pays out before the option is there for them to play again. Besides, 12 hours is the maximum, so a single player could play the same RG more than twice in a day if it turned around quick enough.
As long as the RGs are varied in both courses, conditions (I'd like to see more variation with green speeds like there used to be) and Credits, I don't think people can have too much cause for complaint.