I can only speak for myself but I stopped obsessively checking Slashdot (which had been a habit since 1998) around mid-late 2006 when Digg/Reddit had started getting momentum and interesting stuff was showing up sooner there since content wasn't curated.

Now I look at Slashdot maybe once a week, and I never read or participate in the comment threads -- because a given story on Slashdot likely showed up on HN three days prior and had a more interesting discussion then.