the rule of thumb in the textbooks used to be 1 month out of RGPs for each decade of wear. in reality, this rule is overly conservative, and you don't need to wait that long
i am recommending a newer rule of thumb, which is a month out, then do a topography or orbscan or wavescan to check for warpage
it's not the time out that matters, it's however long it takes to unwarp
the tricky thing is after RGPs your astigmatism actually goes UP in the unwarping process, as compared to soft lenses, where it goes down, so your doctor needs to know this and wait for your astigmatism to increase to the max value (kind of opposite)
hope this isn't too confusing :)