^That's possible, as Kirk's line about being stale may not have been in reference to his commanding a starship but to doing any sort of fieldwork. Perhaps he had another type of hands-on assignment after the five-year mission ended before his promotion to admiral.
There's also his statement to Decker about his five-years' experience being the rationale behind his decision to command the V'Ger mission. Perhaps he meant his five years in deep space as opposed to his five years as Enterprise's captain. Maybe the Enterprise was assigned to border-patrol duty for a period of time after her five-year mission ended but was eventually recalled for her refit.
Both of these scenarios would push back the date of TMP, but neither would invalidate the timeline based on the films alone.
--Sran
There's also his statement to Decker about his five-years' experience being the rationale behind his decision to command the V'Ger mission. Perhaps he meant his five years in deep space as opposed to his five years as Enterprise's captain. Maybe the Enterprise was assigned to border-patrol duty for a period of time after her five-year mission ended but was eventually recalled for her refit.
Both of these scenarios would push back the date of TMP, but neither would invalidate the timeline based on the films alone.
--Sran