I love my job, but still I often don't want to go. As jobs go I wouldn't change it, but nor would I do it if I won the lottery.
In some ways it's harder when you're in a position of choice!
Are you already booked or will you get a call tomorrow if needed?
I'd hate working like that. I like to know what my day holds & 'the call' would always feel like a massive intrusion!