In the original timeline the five year mission was full of action. If we assume all TOS episodes take place in the 5-year mission and that they span over the full five years, I guess every 2 weeks the crew of the Enterprise and mainly Kirk had to deal with red shirt death, tricking god-like entities or computers, ripping of his shirt and fighting bare-handed against alien creatures, saving one planet and culture after the other.
This takes not into account the possibility that there where even other interesting events and adventures that are not shown on screen.
In the new timeline we see in Star Trek Beyond that the Enterprise has finished 3 years of its mission. We see Kirk on a diplomatic mission that fails and by his reaction we can guess that this is not the first mission of this kind and with this outcome. From his log entry we learn that he seems to be bored and disappointed and one he does not now when one day ends and the next starts.
So what about all the planets, entities and events that lead to the Enterpise adventures of the prime timeline? Where all the challenges still not discovered yet? Are the solved by antoher ship? Are they non existent in the new timeline?