The sandbox started roughly one year ago. First it lasted about 2 months, currently it seems to be lasting between 6-9 months. It works like this:
new site is launched.
site jumps very high in rankings for its keywords. This is known as the 'new site boost'
After a few weeks, the site plummets, although if you use the various allin tools provided by google, you can usually find it where it should be.
