All Academies (except USCGA) utilize “rolling admissions,” which means each day that goes by, it’s more difficult to get accepted. All things being equal, you want to be the first application submitted to have the best chance.
They usually give acceptance letters as early as January until May, on a “rolling” basis. As Academies give away more slots, your chances of acceptance go down.
In fact, Academies offer 100-150 Letters Of Assurance (LOA), which are offers of acceptance contingent upon a nomination and medical clearance. They only give these to applicants who submit early (Aug-Sep timeframe).
Even worse, DODMERB gets backlogged after January, delaying your decision even more.
The advantages of submitting early are clear: beat your peers, get an LOA, get medically cleared, win the appointment.