Condensation can be an issue inside the plastic bag. As I'm still at the laggy-band-around-the-arm stage (which led to Jim Gresty commenting "Oh, you must be a devotee of Flat Earth Bob"), careful positioning of the band so as not to obscure the instructions is also essential.
I usually carry a spare laggy band, too - and more than once I've given them away, including when people's devices have given up the ghost/made a bid for freedom. Handy things.