Login cookie expires quickly and in a rather inconsiderate fashion

I'm rather baffled as to why the site won't allow you to stay logged in, it's not a financial institution, but hey, security.

What is really rather annoying is that you get logged out while you're using it. Is it too much to ask to have a rolling 24 hours rather than, "yes, I see you're reading the site, but it's 24 hours since your last login, so it's authentication time again"?

I seem to get a rolling window. I only get logged out when I haven't been on the site for a while. As long as I visit regularly, I can go forever without needing to log in.