3) Descent/landing
The primary consideration here is the old question of shock cooling, and whether it is best to pull the power back slowly or if it matters. As with above, dynamic counterweights don't like rapid changes in power, but certainly going from cruise power to idle in around 1-2 seconds won't hurt anything as far as counterweights go.
The old rule of thumb with shock cooling is to reduce power 1" per minute to keep temperatures reducing at a reasonable rate.
Now, there are a few things to keep in mind here. The first one is that, if you are doing what was outlined above to keep your CHTs/EGTs/TITs low and happy, that will also mean that the difference between operating temperature in cruise and at a descent/approach power is minimal. I think that the shock cooling issue probably came up more with turbo engines that were being run hot and hard, and were therefore more susceptible to damage from a rapid temperature change. Meanwhile, an O-360 seems to have no problem getting power cut to idle rapidly all day long in the pattern with students. Either way, the theory about shock cooling is that it will typically manifest itself not in cylinders falling off, but gradually with decreased longevity over time, cracks in the crankcase, etc.
My opinion is that gradual power reductions and allowing your temperatures to drop slowly to prevent what is known as "shock cooling" makes sense, regardless of whether or not it is the plague some make it out to be. Again, it's more professional and passengers like it more. Plus, it makes sense that letting the engine - the whole engine, which goes beyond the CHTs, EGTs, and TITs - cool gradually can only be beneficial for it, or at the very worst not help at all. So I would advocate decreasing power at 1"/minute roughly, and behaving as though shock cooling does exist.
I also typically will push the mixture full rich (gradually) and/or open the cowl flaps when the landing gear comes down. Gear slows the plane down, and then pushing the mixture to full rich helps to keep the engine about where it was for CHTs despite the reduced airflow, and also reduces EGTs/TITs, and lowers internal combustion pressures, cooling the pistons. An engine monitor is the biggest asset you can have in helping to determine what the true temperatures are in your aircraft. Most factory gauges aren't particularly accurate and give you limited information at best. As an example, the engine monitor in the Aztec taught me that when I put the gear down I should open the cowl flaps to full to keep the engines cool. On the 310 there are no cowl flaps, so I push the mixtures rich.
