My oldest villager, Samuel Founder, lived to his 70s even with only lvl 2 medicine, but I was really sad when he died. I encourage breeding of that type of villager and think of them as his descendants. I also tend to become fond of the doctors, mostly because I pick the "handsomest" (someone get me a straitjacket) male villagers and dress them in my favorite outfit (the *really* colorful one).