I don't know about asking schools to wait for your scores, but I'd recommend taking it earlier too... You've seen this schedule, right?
(http://www.ets.org/g...eral/scores/get)
I'm going to spend a little over two months preparing, also while working full time. At the moment, I'm studying 4-5 days a week, an average of 2 hours a day on the days I study, although I need to ratchet it up a little soon... In addition to that, I study vocabulary from the Barron's GRE Vocabulary book or iPhone apps and read dense books that include lots of GRE words during my 1.5+ hours of commuting each day.
Good luck! But seriously, it would make me way too nervous to wait until the last minute to take it!