In Marine Academy: Military Roleplay on Roblox, the game page says training expires after 48 hours , which is the clearest time limit shown there.

If you meant something else by “a hour”:

  • A real hour is always 60 minutes.
  • In-game training sessions or tryouts may have their own schedule, but that depends on the specific event or server rules.

If you want the exact duration of a specific Marine Academy activity, tell me which one: training, tryouts, or a rank session.