In a given hotspot installation, it is very likely that many users will drop by, purchase a specific credit package (1 hour, 1 day, 1 week etc.), and at some point move on and never be seen again.
Think of a coffee shop, or hotel etc. where travelers use the hotspot.
Very quickly, the usermanager database could have hundreds of users in it who are long gone, never to be seen again.
Is there some method that users who have zero credits left, and who have not been seen (last-seen) in say the last week, or month, or six months, could be bulk removed from the usermanager database to clean it up?