Exhaust manifold temperature...clarification please

[JMBT]

So, I am watching my exhaust manifold temp gauge like a hawk while climbing. With a typical load, not super heavy or super light, on the big TX hills, and its 96 degrees outiside today, I can either:

A) Hold my speed steady to the top with no gear drop, at top temp is about 930, as I back out of it, and kick on my manual fan switch to cool down.

B) Hold top gear until RPM's drop off a bit then hit my fan switch and grab a lower gear. I'll top the hill about 8 mph off my starting speed, and temps about 830- 850

C) Flip manual fan switch at bottom, drop gears and speed in succession, to keep manifold temp gauge in the 700's and RPM's high.

So, conventional wisdom says the cooler the exhaust temp the better on the engine right? However, I have also seen on posts where it was stated that in a high torque application, if manifold temp is too low too much heat may be staying in cylinders, and damaging them?? Did I read that correct? Just trying to figure out how best to run the motor that will extend the life as much as possible. Any help will be appreciated! Thanks.