One of my former roomies had a golden compromise: an allotment of vacation days but UNLIMITED sick days. So he would plan vacations and whatever whatever, and never have to worry about leaving time in case he fell ill. It was magical, as far as I could tell.
I was very ill this year and I will have burned 15 days off. One of my jobs has an unlimited sick days rule and the other does not. (One of them has no vacation days because it is an opera and that explains the unlimited sick rule. If you get an opera singer sick, you are basically fired. Their bodies are their instruments so you must keep your germs to yourself.) The unlimited sick days rule has truly been a blessing to me.