My new job lets me work whenever I want.

There's a shift board, and they let you know what's happening a month in advance. You either sign up for a date or you don't. So if you want close to 40 hours you can get it, and if you want less you sign up for less things.

As long as I don't bail on something I've already signed up for, I don't even have to tell anyone if I want to take a vacation.