Except winter when heater is on, it's nearly always over 50-60% (and up to 75). I almost never dry my filament, but i work most of time with one open spool at a time. Once opened, my spool last between few days to couple of weeks. With high humidity (65 and over) i usually start to get strings after about a week. Never had strings with 45% humidity except spool that arrived already humid