> Your 20′s lay the groundwork for success in the rest of your career.
Can also be said as: While in your 20's, you should start living like you're in your 30's, 40's and 50's, so you can do that and only that for your entire life.
I completely reject that way of thinking.
There are many things we all want to do in our 20's we will not want to do later in life, which is all the more reason to do them in your 20's, lest you never get to do them at all.
As anecdotal evidence, I spent 2 years of my life from 27-29 driving from Alaska to Argentina, because I wanted to. Will I want to sleep in a tent for >500 nights when I'm 50? doubtful. Am I extremely happy that I did? You bet, best experience of my life. Did it "harm" my career? No, I'm working right now as a Software Engineer.