Keeping them on is cautious. They take longer to humidify but they also take longer to dry out, which is a big advantage. The wrapper leaf is protected. If you are very meticulous, you can avoid all the pitfalls of removing the cello and maximize the benefits. Just be extra careful and there won't be problems. For those who are accident-prone, like me, think twice before removing the cello. Mike H received some of my mishandled cigars in a trade. Had I kept the cellophane on, I doubt they would have had a single blemish.