Sealed Headphones vs. Leaking

Leaking is a big problem when recording, especially with quieter passages. What is leaking?
Leaking means that you can hear a bit of the headphones on the recording. Some people then proceed to use totally sealed headphones. But these make your players play badly because they cannot hear themselves when wearing them. If you have big problems with leaking and need to use sealed headphones, at least let them wear it only over one ear and leave the other uncovered. If you have the technical possibilities to do so, better automate the headphone mixes so they go down on very quiet passages and go out nearly completely when the players have a very long break (you can of course just edit those parts out anyway). You can have them come in with a count-in a few bears before the player has to resume playing. This is complicated, though and you need to make sure the technology performs up to your standards!