goodroi - 5:22 pm on Dec 18, 2012 (gmt 0)
There isn't really a formal sandbox with a mandatory time period. It is more of minimum quality signals that Google is looking for.
If you know what you are doing you can get a site in a non-competitive area ranking relatively soon. In my experience most local business websites are not managed by smart webmasters and thus many of them never develop quality signals so they never rank.