I often have the bulk of my ranking officers retire from disuse before I really need to field a sizable navy. Then, when I do, there's nobody but green junior offices in the entire empire!
I was wondering whether creating a bunch of 'fake' teams and task groups at the start of the game to preserve quality officers would be useful. Then when you field a sizable navy, disband the Not Actually A Geology Team and Task Force Lying To The Budget Office you've got your top brass! They might need to take some serious phys-ed to get back into shape, though...