Let me tell you a little secret about vacation time.
Companies don't give you time off because they want to be nice to you. They aren't doing it to be charitable.
They're doing it because you're difficult to work with when you are stressed. Let me say that a little more forcefully: when you postpone taking time off, you become a pain in the ass to everyone in the office, and we don't like working with you. You're irritable, difficult, and disagreeable. SO TAKE TIME OFF, DAMN IT!
Sorry for yelling, but it's for your own good.
A successful vacation takes your mind off work enough so that it can relax. It may take several days to forget about work enough so that you are in full relaxation mode. Only then can your body repair itself. I need at least three days to get to relaxation mode, and then six or more days of relaxation to really feel refreshed. Add a couple travel days and a day to get back into the swing of things, and we're talking 12 to 14 days for a really successful vacation. You deserve at least as much.
Let's look at some common vacation mistakes that system administrators make:
Using an occasional vacation day to run errands, do laundry, etc. That's not a vacation. That's using vacation time, but it doesn't meet the goal of relaxing. Maybe you can use comp time for errands or come into work early and take an hour or two off during the day to run errands.
Taking a long weekend. That's sort of like a vacation, but it skips the multiday process of getting to relaxation ...