There is no way to know which finals will be offered during which periods, or what time the final periods will be, until the schedule is released. Once the schedule IS released, cadets can move their finals around (within the specific periods each is offered) to fit their needs, ie. want to leave USAFA as soon as possible, only want 1 final per day to increase study time, etc.
Additionally, the number of finals a cadet will have varies based on the classes they are in: some cadets may have 2, others may have 6. Cadets can also validate certain finals, but won't know if they did until a few days before finals begin. Cadets may only take 2 finals/day.
Therefore, a cadet may need 1 day to complete his or her finals...or they may need 5 days. There is absolutely no way to know at this point.