Doing my first 24+ hour cook, and the biggest hunk of meat yet (beef brisket, loosely based on the CS video posted last week), so using a much larger pot than hitherto. I'd seen other people post about putting together a foam lid to minimize evaporation, so I thought I'd try that out for myself:

I cannibalized an old camping mattress for the lid, then decided to go ahead and wrap the whole pot on the theory that this would reduce the energy consumption over such a long cook. Five minutes and a pair of scissors is all it took.
The plastic clips are holding the bag in place, but they kind of ruin the look, might need to upgrade to something sleeker. ;-)