I have never experienced any flat spotting this past driving season. I have the PS2's with 19" Carrera Classic wheels and my car has sat for periods as long as 2 weeks between drives. Lucky me!
I have it parked now on very dense rubber pads for winter storage. Bought 4 rubber tiles at Menards for $52 and cut in half. I plan to move the car, by hand, at the beginning of each month about 12 inches to another spot on the tile and tire, and then move back the next month, and keep repeating until March. So, hoefully I won't have any flat spotting during the 5 month storage period. Or maybe I'll have 2 flat spots per tire!
I am also running nitrogen fill, with the over-fill to 58-59 PSI for the storage period.