What I'm saying, is that RDY requires you to get back within :20. The odds of that call happening are very low. When I was on reserve and had to do airport jail time, I left but made sure I could return within :20. Paying to park is merely a backup option to ensure that I wouldn't be late should the uber-short phone call come, but I never had to do it. Its an investment in sanity to be able to hang out elsewhere. There are several pleasant downtown areas and parks nearby to enjoy, maybe run an errand or two, and then be on your way close to the end of the RDY 'shift'.