That is a pretty good average humidity, he'll need to be misted about three times a day on average, and that should be with a dripper, I would mist for about 2 minutes at least. If he's still drinking after that two minutes, you might want to consider misting for 30 seconds longer. I mist my jackson for about 4 minutes and so my panther gets misted the same amount, he is less thirsty than her, but my jackson gets stimulated to drink slower and drinks for longer than my panther does. They both get misted 4 times a day.