I am an admin, and I'm not sure either, or at least I'm not sure it's a board problem.
The log in status when you click "remember me" is stored in your cookies, in ie there are settings that control this in the security and in the auto complete pages, so if your losing it, it's possible that is getting deleted. usually after deleting my web history I have to log in again myself, but that's just how things work.
There are certainly no admin settings pertaining to this system, it's part of punbb automatically, ---- as I said I use it myself and other than when updating history it tends to work fine.
Then again, there was a period when it refused to work at all, i think due to some changes microsoft had made to ie at the time, so I think it's just another case of microsoft's insane security, that our old mod Cx2 once described as putting five locks on your door then leaving the key outside under the mat .
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)