I mean, once they mastered research or farming or healing, do you put them onto another subject or are you keeping them as THE Master Doctor, THE Master Scientist...?
I play a few differnt ways, one time I might try and keep everyone with knowing just one thing (although that takes major mico managing)
Another time I played where once they advanced from one level to the next I moved them around to each area to learn (with the exception of breeding, of course). This way also took some micro managing.
After winning the first time, you tend to try new ways to play the game to see what you can come up with.