I don't leave mine in for more than 10 minutes - just until they are crusted over on top. I am sure you could safely leave yours in longer due to the humidity but I don't know how much longer. I read this post (http://www.lilaloa.com/2012/06...hat-you-need-to.html) by LilaLoa and she was in a super humid area at the time she wrote it. I hope this helps you and I look forward to hearing about your results