Something that might help with Hacker News is the “noprocrast” settings—you can configure it to only allow you to be on the site for a certain length of time and then not let you back on for a different length of time. If you configure a 15 minute “maxvisit” with a long “minaway” (600 minutes?), that might accomplish your goal. One problem with the feature is that it doesn’t kick you off a page you’re already on if you’re scrolling through a long comment thread (and obviously won’t help if you just open a bunch of tabs), but at least it forces you to stop on some behaviors.
Something that might help with Hacker News is the “noprocrast” settings—you can configure it to only allow you to be on the site for a certain length of time and then not let you back on for a different length of time. If you configure a 15 minute “maxvisit” with a long “minaway” (600 minutes?), that might accomplish your goal. One problem with the feature is that it doesn’t kick you off a page you’re already on if you’re scrolling through a long comment thread (and obviously won’t help if you just open a bunch of tabs), but at least it forces you to stop on some behaviors.