Guys,
My chief engineer (Navy with a strong dash of Rogue tossed in) had an incredible series of rolls on his fourth term. He got battle duty (and survived barely), got the Starburst for Heroism, got promoted to Chief Warrent 3 (my GM allowed me to get an Imperial
warrent rather than a commission...but the warrent terms counted as officer terms for muster purposes), and got a good roll on extra XP.
Finally, when it came time to roll for reenlistment, I got a '20'. [I was rolling hot for my 4th and 5th terms.]
Why my GM and I came up with is that Gani (my character) in the heat of battle came up with an unprecedented way of using the
jump engines to help restart and contain a failing fusion reactor core. It killed half the damage control party, but it worked and saved the ship. Of course Gani was working "by feel" and even to this day
he still has no idea of exactly how he did it....but that did not prevent the Imperial Navy from holding him over an extra term to try to find out themselves

[Gani grew to
loath a certain BuWeaps Admiral during the debrief as well.]
The point is that while it might not have been what I might have chosen, it worked out well for the character concept.
-Polaris
P.S. My thoughts about
balanced prior history are well known, but I have to admit that rolling for the details of your prior history can be a lot of fun.