For what it's worth, I watched the movie again last night, and it's very possible to explain more time passed between going to Earth and Kronos than was shown on screen. There are cuts where some more time could've easily passed between the events being shown.
And of course, there's this old chestnut: The ship travels at the speed of the plot. It's as patented a Trek writer's move as having the transporter broken or unable to be used at the most inopportune moments just to heighten the drama.
The way it's done when they're going from Earth to Kronos, I could believe that a lot of time had passed on their journey because of the way scenes played out and you could assume a lot had happened between Spock's praising of Kirk's decision and him confronting Carol about her status on board. However, what disproves that is when they're heading back everything happens quickly without implying that much time had passed.
Besides, in the past a captain's log was all you needed to show that time had passed in their travels and at the same time keep the pace going.