Best timer settings for reptifogger?

Hello, I just got a reptifogger and I timer, and I'm wondering what the best settings would be (ie. 30min on low mist every 4 hours). I live in a NH so cold and dry, and I am not home enough to mist it as much as it needs. I have my 5mo old BP in a bioactive 20gal long tank, 90°F on one side and 75° on the other. But the humidity drops down to 10%-20% every 2-4 hours. I've tried to keep up with it with a sprayer but I fear going from 70% to 10% several times a day is not good. Any help is appreciated.