I always start in 1939, with realistic career enabled. Then, when I'm retired, I make a note of the port, the type and number of u-boat, and then assume the identity of the replacement captain & crew for that boat. I continue thus until the boat is sunk.
However, since GWX2.0, I've not had so much time for playing. I've completed 2x Type IIA missions out of Kiel. But I was thinking about retiring crew members after a certain number of missions (transfers to other boats, assignment to desk/staff jobs etc.) to ensure that my crew doesn't get too good.
Does anyone know what the crew turnaround for officers/NCOs/sailors was in real life?