Don't worry about the bookmark collection you already have. There's no pressure to read through it and no pressure to throw it away. That's the great thing about a digital hoarding habit -- it doesn't fill up your house and disrupt your life like physical junk would.

If you're concerned about the time you spend scanning through HN and creating the bookmarks in the first place, what you should do is replace that activity with something else. Concrete example: I decided to eat less junk food, and the way I did it was by filling the fridge with healthy foods which I could eat whenever I got the urge for a snack. It's much easier to replace than abstain.