I really enjoyed learning about hifi audio and acquiring ever-improving components when I was in my late 20s...and I'm now 70. By the time I was in my late 30s, however, I was in a similar situation to many - if not most - people: things had emerged in my life that were clearly more important. My priorities were no longer just my own interests, but the wellbeing of my wife and children, and the establishment of a degree of financial security that would enable our family to survive the challenging times that will face most of us at some point in our lives.
That meant that I not only stopped devoting as much money to my audio hobby, but also spent more time at soccer games, school plays, family conversations, etc., and less personal time listening to music in my home.
Now I've been retired for about two years, I've started to acquire both good equipment and good recordings again, and I'm finding time to disappear into my listening room for a couple of hours a few times a week. My hearing may not be as good as it was 40+ years ago, but I still find immense pleasure in good music reproduced well, and I still appreciate the nuances and emotion revealed and reproduced by excellent gear.
So for me, stopping upgrading isn't defined by my equipment, but by my circumstances and those who share them. I suppose I've been frustrated a few times when I've wanted something that was unattainable due to competing priorities, but I've never second-guessed my valuing my family, faith, conscience, or wellbeing above a new DAC or cartridge.