When I am logged out, I still see a count of notifications and am able to list the notifications. This occurs after I've timed out on the 'remain logged in for 48 hours'. The login box retains my username but I have to log back in.
Hey - it's nothing to do with me! I thought I got away with being called Cookie back in school - and now I get blamed for this! Harummmmphhhh! I still have to talk to my shrink about being accused of being a 'monster'.
At least I had some power with the 'Simon Says' game!!!
I just followed up with the engineering team and the authentication system is working as designed.
There are two levels of authentication and time periods associated with each. One of them lasts 48 hours, the other 30 days. In general you need to be within the 48 hour period to post, comments, publish, edit, etc.
So as @WryLilt pointed out if all you are doing is browsing and reading, then you may not need to login actively for up to 30 days, but will be asked to login for some actions.
There are also cases where you will be asked to login more often (shared IP, much activity from the same IP, etc.)