The one thing I've always told employers when I go on vacation is to treat my absence as though it was permanent. What would they do if I was leaving for good? They can't hire someone before I get back, so, treat the absence as though they were between my leaving and hiring someone else. That gets them and me thinking about what needs to be accomplished prior to vacation. This usually works unless something major breaks. I'm always on call for that sort of thing. It's the nature of our profession.