Don't sack wounded gals! That's the peak of women exploitation! ;P
Recovery time can get ridiculous in Piratez. I've seen up to 76 days. But it was a good gal and their monthly salary is not expensive ($5k/month I think?) so it's not a big deal once you have more barracks. As Dioxine said, it is common for me too to have 1/3 to 1/2 of my gals wounded at the main base.
I actually have started to do a "gal rotation" on the Bonny, where I rarely take all my best gals at once. That way other gals can get some training, as well as some chance of getting hurt instead of my best, and I almost always have good gals to bring on missions.
Too bad there can't be a facility that decreases recovery time (something like each days count as 2?)