Can Centova be set to auto-disconnect after a specified period?

And if so, does it depend on which player is being used to access the stream?

I'm wondering about the situation where a user stops active listening, but remains connected and thus reduces available streams and bandwidth.

Unless you are a mind reader, there isn't a way to see if a listener is connected but not listening to your stream.

Some broadcasters set a time limit on how long a listener can listen before being disconnected and have to re- connect.
Control Panel > Configuration > Settings > Advanced > Always disconnect listeners after ?? minutes (0 for never)

Thanks.

From a practical viewpoint, the percentage of 'absent listeners' is likely to be small - and hence it's probably better to  accept such wastage rather than inconvenience active listeners.