It wouldn't have worked to make it more than the 1 year, this Trilogy is "The Hero's journey".
movie 1 - Hero/Chosen One is thrust into a Destiny/Leadership Role before he's ready, because of his potential
Movie 2 - Hero shows his leadership weakness (still too reckless) and completes his transformation to "The Hero" when his Mentor is killed and finally earns his position by the end
If it had been 4 years in between, that's far too long for The Hero, not to have gained the Leadership experience to not be so reckless and reactive.
well if we're going with the Hero's journey then we should look at star wars take at it's timeline
The Empire Strikes Back takes place 3 years after Episode IV. and Return of the Jedi takes place a year later where Luke seems to be a more experience jedi and seem to have hone his jedi senses to where he can take on Darth Vader and the emperor.
if they do this with James Kirk then the third move will show him at a time where we see him at a time where he is more experienced and more seasoned and not so reckless.