I've only been running my Phantom for a day, without it being publicly listed, and I'm already noticing that some users are not disconnecting.
This is a problem if you have limited internet bandwidth or a limit on monthly use.
I think some time limits are required, as is the case with the KiWi.
Inactivity - When no changes are made via the browser GUI for a period of time, say 1/2 hour or 15 mins.
Daily - The amount of time someone can remain continuously connected for in a 24 hour period, say 2 hours.