I was using a MUD client called ZMUD to test this, which I've let idle for hours at a time on other various MUDs out there (edited to say: without any problem or booting, of course.)
Also, may I point you to [link]
The telnet inactivity boot is discussed in-depth there.
Hmm, that's very interesting. I wonder how I missed that thread six years ago!
I did a quick investigation and I am seeing some code that looks like it might be used for this purpose. We'll have to do some testing to see what exactly is going on, but I'm sure it's fix-able. My gut feeling is that the telnet protocol is supposed to boot inactive clients and our code respects that. However, keepalives (which are probably used by your client) might not be triggering anything on ours-- we should be able to fix that. If that's not the case, we'll just set it up not to boot (or at least not for a much longer time).
Also, may I point you to [link]
The telnet inactivity boot is discussed in-depth there.