I do the same with my 14 years old villagers! When I quit the game I select
two villagers as doctors (one doctor could be sick himself, so it's better to have 2!) because if they are not select as healer they don't heal anybody by their own, you have to bring them for doing that
After the villagers are selected, I put them on a task as farming or research, etc and they'll do it! And so I may leave them and be quite. If all my villagers have any healing skill, it's easier to choose the 2 healers!