"Recess appointments" are one of those things that has lost a lot of its meaning over the years. A Senate recess might have meant something when members of Congress had to travel for days or weeks between their home states and the nation's capital. With the advent of air travel and the ability of Congressmen to travel anywhere in the country within hours, that has pretty much gone by the wayside.
It's interesting that a radical leftist like Stephen Breyer wrote the majority opinion in the case against the Obama administration over those NLRB appointments.