My personal opinion is for the simple 4 cylinder engines fitted to your typical club trainer/tourer it is pretty much a non issue.
I think the reason for that is elsewhere:
Most flight training (UK, anyway) is done with full-rich mixture all the time, so the engine doesn't get that warm to start with.
Also many of the higher performance aircraft have less air going into the cowling, because air going down those holes means drag.
And the slower aircraft have less potential for shock cooling because the air at 100kt has a much smaller cooling effect than at 150kt+.
So I don't think it is exactly engine type or size related. For example the 360 is the same as a 540; just 2/3 of the length. It has the same cylinders,
AFAIK. Maybe the 0-200 type engines are more robust, due to smaller cylinders but the metal is the same thickness as the bigger cylinders?