Adobe defaulting "stay logged on" is a security issue

User error can always be a "security Issue", such as a user not unchecking that default.  I'd say PEBKAC.

On the other hand, I haven't been logged out in months.

This is a security issue.  It doesn't matter if the user is logging on from their own private computer, or from a public computer, this is a security issue that should be addressed. ^_^

You don't have to be worried about this. These forums will log you out after some time when your system is idle with no activity at all.  Some times I have to login 3 times when I am on these forums.  Security is their highest priority  and up to now they can be commended for what they have done over the last two years.