Coding AI "Needs"

So this past week I've been working on making the AI have "needs". It's currently rather simple now but effective. Characters on the space station now need rest and food. Without either for too long they'll suffer ill effects. Marines become slower if tired and anyone who suffers from hunger from too long will die. This has also led me to have to work on space chickens more. I'm currently trying to strike a balance as to how quickly space chickens should repopulate on your station.