They released one new 'Act' of the History each year from 2007-2010 with each 'Act' covering roughly six years of Stern's broadcast career, so it was a bit of a surprise that 2011 brought no Act 5 since it would have covered around 2002-2008. Perhaps the entire point was just to exploit the vintage taped material and rather than get into the Sirius years they just stopped, but hopefully it'll return at some point.