At the bottom of HN pages is a "More" link to go to the next page of links. Often times this return "link expired" or something of the sorts. How long does it take for you to be sitting on a page before this kicks in?
HN is written in arc, and many links point to thunks/closures ("if the user clicks on this link, run the following function on the current data"). IIRC, such thunks are valid until the memory is needed for something else.<p>So it depends on server load; maybe it's time for another memory upgrade.
It's usually around 15 - 20 minutes. Makes me feel like a bomb defuser, having to make sure to get to the next page before time runs out whilst working on other tabs.