Hi Tomo,
I was instructed that we need cowl flaps open when you have high power and low airspeed, like take-off. Once in the circuit for landing, temps should have stabilised from the descent and cowl flaps can add drag for the landing phase (depending on type).
Yes, they also should be ready for a go-around.
At the end of the day, it is easier to have them locked in a checklist than going through more assessments during the landing phase.
Matt