I don't often post as I'm a thread killer
At any rate, I find this thread to be pretty interesting in what others think. For myself, my parents took me on my last family vacation once I graduated HS, before college. My mom said that it was their time and my vacations would most likely be with my friends, experiences, etc. I never was hurt, felt neglected, or unloved. We are all only children, therefore, thinking may be different

My parents took 3 week vacations and started traveling to Hawaii for the 3 weeks. It turned into them being world travelers until my mom got sick and they could no longer travel. My time was much more limited as I had my own obligations be it school, or my job. I started out with 2 weeks vacation and started my own traveling with friends. I got married and we set off on our own journey. Perhaps if we were a family to have a beach house or a place in the mountains, we'd have gone together with my parents, who knows. However, my parents did their traveling and we did ours.
We took our DS on his last family vacation after he graduated HS, before college. He will be graduating college this year, also has been working. He does not feel left out, hurt or unloved. We still have great family time and do things together. However, DH and I have our vacations, just the 2 of us. Again, an only child situation. Many of DS' friends do not go on vacation with their families, even when younger siblings go, as they have their own responsibilities and their time off they prefer to start doing their own things with their friends. Would they turn down a family vacation? I am sure not. However, most of his friends have their own things going on at this point...be it school, internships, or interests.
Many of our friends are beginning their "empty nest" years, not necessarily full time yet as they have college age kids but the "kids" are not home much and they are beginning the next phase of their life.
I don't think that there is any right or wrong ways, just different dynamics, different thoughts.