A five-year mission was a standard mission duration for Federation starships in the 23rd century. For bigger, faster and more enhanced vessels, ships could perform exploratory missions farther outside Federation space, and not need to dock at a starbase so often.
History and specifics
During his career, Robert April commanded four five-year missions. The Enterprise's first one was under his command, and prior to that he conducted three missions in command of the USS Tiberius. (EV comic: "Flesh of My Flesh")
The USS Enterprise under Captain James T. Kirk was the first ship that was given the first five-year mission. However, the five-year mission briefly ended with destruction of the Enterprise at Altamid. The mission would resume after the construction of the USS Enterprise-A. (TOS movie & novelization: Into Darkness; TOS movie: Star Trek Beyond)
- USS Tiberius
- three five-year missions
- USS Enterprise
- USS Enterprise (Kelvin timeline)