I've been with my employer for 15 years, since the 4th month of it's existence.
We (those of us who've been there 15 years) now get 4 weeks vacation and 3 sick. We are able to sell back the 3 sick at the end of the year and up to 2 weeks of vacation.
When I first started, I worked a 12 hour schedule.
4 nights on, 3 off. 3 days on, 1 off
3 nights on, 3 off. 4 days on, 7 off
So I had a whole week off every month that was built into getting 40 hours per week (36 hours plus 40 hours and 8 overtime for the pay period.)
Back then, I was single and had a week off every month anyways, I rarely took vacation time and sold majority of it back and always sold my sick time back.
Now I'm married, work steady 5 day /week daylight, and I have kids who are sick constantly and at least one trip to the hospital overnight every winter. I have house projects in the summer, and we just went on our first vacation as a family last year (2 vacations actually, Disney and the beach.) So now I take all my vacation and sick time, which is 4 weeks and 3 days sick.