I think once every 15 minutes would be nice. Some of the gates give you 10 minutes to complete them, so chain running them with no down time in between wouldn't be great design, I think. On Serpah, the Golden Saucer has been much more social lately in between the 20 minute gates and I personally wouldn't want it to just become another place where we spam queue for leap of faith, slice is right, etc. with no down time in between. 15 is a good compromise.