If you're smoking Friday night, I would rub late Thursday night after you're done with your thing after work.
Like previous posters said, you can certainly do two days in advance, but it will almost be like a paste by Friday.
I prefer water in the pan for long smokes, some use a clay saucer, sand, etc. for their heat sink. Whatever you use, it will stablize temps when you settle on your vent settings.
If it's your first overnighter, you're probably not going to get much sleep. I usually get about 5-6 hours. I get up a couple times to check on things and see if I need to add more water.