Silent Hunter III Iron Man Rules

Originally Posted by CWorth

3. After my 5th patrol I will roll a die to determine whether or not I will retire from my career.Evens means I continue for one more patrol and then I roll again after that one..Odds means I end my career right then and there.

I was wondering, were UBoat captains given the option to retire from patrols (after 5, for example) in real life? I'm guessing yes.