Note that I said "when", not after

.
But, yep, you're getting the drift now. You can't state a number because every individual installation is a little different. Also, you can cover PART of the cooler, up to ALL the cooler, depending on temps.
So, every time you land for fuel, remove a bit, or just take it all off if you're worried about it. Won't damage anything to run slightly cooler temps.
This is one of the problems you run into when flying through changing air temps, and you just have to deal with it conservatively.
MTV