I do what Jim does, I just in my head keep a general idea - for example:
I put in 20.00. I spin for a while, and keep rough track of my little wins. Then at some point, around 15.00 I start checking my personal banker regularly to see if if the transfer button shows up. Note that if you've played enough to get a 1.00 free play, you actually have to check that room transfer (whatever it's called) is available.
I then start checking every few spins.
That said, I like playing and since it's cumulative over the whole cruise, I probably could straight cash out, but I like to play some. Lately I've been winning a bit, so I cash out when I'm 2.00 over what I put in. I think I'm getting a lot of bet collateral.