I think everyone does things differently , seems to vary with weather,location,breed ,make of incubator etc. Personally I run mine dry untill nearly all are pipped then add a little water or move to hatcher---if I havent managed to move them to a broody hen .The polystyrene box I use as a hatcher seems to keep humid enough and I dont add water in there. Mine never runs as high as 70% as I am sure I have drowned more chicks than Ive dehydrated! Im afraid its all a bit trial and error till you find what suits you. Good luck!