My longest trip was a solo backpack trip to Europe at age 24. I had friends in both Dublin and Glasgow and could use those as a home base as needed. 13 countries on a EuRail Pass, total of 5 months. Lots of bread and cheese, this was by no means a luxury vacation but eye-opening, exciting, and fun !
I also spent 20 days in Hawaii, spread over Oahu, Maui, and Kaui. Actually, it was two travel days on both ends so really just 16 solid days/nights in Hawaii itself.
I'm partial to 10 day vacations, they seem to work perfectly for me, whether it be a cruise, a Disney vacation, or an international trip. If I can manage it, I try to get away at least three times each year but also take a 10 day staycation right in the beach town where I live during July.