I took 2-3 week vacations several times over the last ten years of my career, primarily for 12-14 night cruises. When I retired, I had 400+ hours of vacation time banked (just shy of my max of 2 years accumulation). After 30+ years, I was getting 2.5 days a month, and my boss could never "be without me" for more than a few days. A couple of times she tried to refuse signing off, but when I explained to the department manager that my father's birthday was in March, and I WAS going to be there for his birthday, my boss had to back down.
I tried to use up the extra house by taking either Monday or Friday off for a while, but she insisted that if I was going to take one day off weekly, it had to be Wednesday. So I used the bare minimum to stay under the use it or lose it level, and made her pay out my vacation time when I left. I'm vindictive like that.