The quicker they feather, the 'hardier' they will be....reducing the amount of heat greatly intensifies feather generation.
It's a double edged sword...keeping temps at bare minimum an at the same time trying to keep them from getting chilled. If the temps are kept high, it will take longer for...
Yep, but each of us use what 'works' for us....it may or may not work in other situations, it's a general guideline that has worked for many breeders for many years!
At 1 week old the temp in the brooder should be around 90°F. The temp can be lowered by 5°F per week until fully feathered out or the ambient temp is 70°F.