I have in my contract that parents get at least 4 months notice before I take holidays for 7-10 days. For 2 weeks off, they get 6 months and for anything over that, a year. This gives them plenty of time to sort out their childcare. While I'd love to take the same period off every year, I also love to travel and do so according to cheaper airfares. Currently, my fav trip is camping in Culebra, Puerto Rico, so for 3 yrs now, I've taken roughly the same time frame to land in with mainly other backpackers, but that could change should I find another little island that tickles my fancy. Really, with enough notice, parents should be totally fine with figuring out back up. Everyone seems to have a different way to handle vacation time and all of them sound perfectly reasonable. Do what works best for your family.....and your sanity