Is nighttime lowering of the heat pump sensible?

That means when the temperature drops, the pump first has to work to raise the flow temperature.

But only if the house has cooled down, for example due to unnecessary nighttime setback.

If the pump runs continuously, it has less to do. Because it only has to compensate for the slightly higher heat losses caused by the cooler outside temperatures, and nothing more. And not run at full power in the morning to make up for what was lost during the night.

..and the heat pump, at least mine, operate with a smoothed outside temperature. Once properly tuned, see berny's post, it should really regulate itself. Mine only gets briefly "out of sync" and makes it too warm/cold during sudden and all-day sun or extreme temperature fluctuations. It’s simply due to the low flow temperatures and the associated large storage masses.