Have you ever thought about the concept of "retiring" your officers? Once they reach max level (if weren't already), spend SP to permanently send them off with a lump-sum pension/severance in exchange for bonus experience. Though you can't do it as soon as they capped: once your officers max, they either have to stay in your fleet for a set number of days (recorded) or they accrue enough enemy Fleet Points in battles (that they participated in; personal kills may not be necessary), whichever comes first. Additional considerations include whether (or how many times) you have mentored/demoted/retrained them, and whether they are level 5+.