Although I don't know how long such notifications are displayed, (I would like to know more about it too).
Couldn’t find exactly what you are looking for but found something close to that. Password change and reset-
https://bitcointalk.org/index.php?topic=827927.0I just found that too. It's visible for 30 days, it shows if an user got inactive for 180 days.
You're considered to have woken up if your last login time is 180+ days ago, and the message remains for 30 days.