That would probably work terrifically if there was an eviction algorithm other than crashing at least once per day. (If you try to comment and get "Unknown or expired link", it's because news.arc crashed between the page load and the POST)
links loaded into memory - how does that work? Can you please explain?
Anything that has been accessed within the past x amount of time and hasn't fallen out of cache yet. For more info, check http://github.com/nex3/arc/blob/master/news.arc around lines 1485, 1550, 233.