Okay, STID has it that as of 2260 in the new reality, there has never been a five year mission in the history of Starfleet. Just wondered, are there any books or whatever that posit missions of such lengths prior to the era shown in TOS?
There's been nothing in the 2009/2013 films to say that "Enterprise" did not occur as it did, so you'd have a two-year mission (as I recall, Enterprise, after "Broken Bow" never returned to Earth till "The Xindi"). From what I could tell, the NX-01 model in the 2013 film looked just like the NX-01 from the TV series.
But I believe "Starfleet Year One" had the newly launched Dadelus heading out on a multi-year mission.