Kinda early.
I think people should chill out and announce during summer 2015 at the earliest.
Waste of time and resources otherwise and you are exposed to the media way too early (see Tim Pawlenty).
This exactly the time to be setting up finance committees and the like. The midterms are over and the donor base is looking for signals about where to make their political investments for 2016. There's a reason Obama
announced his run in Feb 2007, and that wasn't even exploratory. The year before the primaries is often referred to as the invisible primary since that is when the candidates spar behind the scenes to line up organizations, endorsements, and especially donations.