So idle logout is going to be a concern here.
In most games, idle logout isn't a big issue -- you can always go back to where you were.
Here, you can't. Your server state is thrown out. State that took you time and potential money to get to.
What can be said about a client going idle? Well, one thing that can be said is that if all the players on a level are idle, the server process / thread handling that can go idle until someone wakes up. It can do a blocking wait on input messages from the client(s).