With regard to the time frame between the flare and the touch down the shorter the time frame the less exposure one has to both drift caused by X/wind and height above the runway variations caused by wind gusts and thermal activity due to temperature changes.
I am cursed with the habit of using logic to help solve problems and thus have come to the conclusion that carrying power through the flare and hold off portion of any landing just exposes me to higher risk of destabilizing the flight path of the device I am flying at the time.
So I almost always reduce power to zero once the runway touch down point is assured.......generally between two hundred feet above touch down to fifty feet above touch down.....
....I find I have better control of the device using inertia as my power source rather than extending the process by using power as a crutch for poor aircraft handling skills......
If I can recall any aircraft fixed wing or rotary wing that I could not land safely and under control power off I will get back to you......
