I don't know if you can still do it, but we always park in the short-term (there are two areas for short-term, but go to the one gate on the left. (It will make sense when you're there).
Anyway, look at the ticket or your watch, and every 25 minutes of so, go get your car and take it out past the booths. If your are under 30 mins, it is free. (This is about 6mths old info here, but i think you can still do it). Anyway, just make the loop again and keep doing this until they arrive. Free parking.
Just a little work.