In my experience, a lot of millenials that constantly talk about traveling and how it "fulfills" them are generally trying to replace that empty feeling not having kids has left them with. It's a biological imperative, after all. The one constant you typically hear from people with kids: "i'm exactly where i should be in the world."

I once traveled every few days/weeks for a year wandering around South Asia. I had a similar realization that traveling is amazing in so many ways but you begin to establish a new normal. The way to break out of the ordinary is through your mind - books, meditation, breath work, etc.