in reply to
prefix 'Newest Nodes' title with number of unchecked nodes
I automatically reload this page every 5 minutes.
There's your problem. I don't think I want to encourage such a practice. 100 users going home Friday and leaving their browser reloading that moderately expensive page every 5 minutes all weekend as the cost grows and grows because they aren't there to regularly check it and hit "I've checked all of these"...
The page has some protections built into it. But those are mostly to protect the viewer, specifically from the page becoming so expensive that it won't even render before their browser times out.