Most big games aim for either March (right before the end of the fiscal year) or November (the "holiday season" but still early enough to be considered for end of year awards). Rockstar buck the trend because they have no competition. They could be competing with a new Call of Duty game and they'll still be guaranteed to be a bestseller. Historically, they would release spring/summer (Max Payne 3 in May 2012, LA Noire in May 2011, Red Dead Redemption in May 2010, GTA IV in April 2008 ) but that's well over a decade now. Really, I think they just have the mindset of "when it's done."