I personally don't handle very much. Usually twice a week for a health check during cleaning and a more thorough check and weighing once per month. I have what i think is a decent size collection along with rat colonies so they don't get handled all that much. I also found that a few of them don't care to be bothered too much so I just leave them be for the most part. My one normal though is more of an ambassador BP so gets handled more, usually to show neighborhood kids and my kids classroom how non aggressive these animals really are.