I think it should ask for every 5 mins. What a lame excuse.
In my opinion, this is the opposite and weakens security:
When a password is asked too frequently, people (including me) tend to switch to weak and therefore unsecure passwords.
When fingerprint is not save, samsung should tell us straight away, but they tell us that it is save for 72 hours, and then, miraculously, not anymore, what a joke!