I think I see the problem....
Circuit power is 15/2300 which allows me to get into the 85kt white arc for the second stage of flap. There is no way that I can fly a circuit at anywhere near cruise power and still get the speed back enough to get the flap in and land.
Maybe in some aircraft you need cruise power to fly an airliner circuit to a massive runway but to fly a normal circuit then you are a very long way from cruise power and thus a very long way from shock cooling when making power changes.
There I am in the mighty C 150, trying to be a courteous pilot in the circuit, fly the 85 knot speed of the rest of the circuit aircraft, and not slow up the works.... 'cause I know there's a pilot behind me flying the circuit at his circuit speed of 85kts with a "second stage" of flap (I'm not quite sure what a "stage" is relative to flap in a 172, the ones I fly are specified in degrees - I'll have to fly a UK one one day, and see the differences).
If I am to countinue my courtesy, and not slow down to my normal home circuit speed of 60 - 50 knots, I'll be flying with a power setting for my normal cruise speed of.... you guessed it.... 85 kts!
When I see how rapidly, even in the summer, my cylinder head temperature will drop off, when I throttle the engine, it reminds me to always treat it with easy power changes, and minimize cold weather gliding. I extend this attempt at courtesy, to the owners of the other aircraft I fly. I have never been accused of cracking a cylinder, and I'm going to try to keep it that way. If others choose to fly differently, that's between them and the aircraft owner - that's why I don't lend my plane to many people!