I was told by the Porsche tech, my 997.1 and 997.2, they should drain for an hour minimum. That way the dealer gets over an hour labor rate for the change.
Since the cars were new, I do my own oil changes. After warming the oil with at least a twenty mile dirve, I let it drain while I check the tires and clean the wheels inside and out. I have a lift in the garage.
With in thirty minutes, it is slowly driping and I replace the drain plug.

 

30-60 minutes.. I go inside, wash up and do something else for a bit.