I think the timeout is a little over 5 minutes after the last page you have seen. If you keep an autorefreshing page open, you should never need to login again. If you close all the pages, or just keep the forum open (which does not autorefresh), you will lose your "connection" quite soon.

This is what is happening to me, at least. As for the reason for the very short timeout, I have no clue

--- Message edited by flying_neko