As of version 2.12.3 it is possible to apply custom xml configurations to Icecast and Icecast KH stations from the Service Configuration -> Advanced tab. All directives entered here are merged into the icecast configuration file automatically. Please note that invalid configurations may prevent Icecast from starting.
This is currently only supported Icecast and Icecast KH, custom configuration support for SHOUTcast is coming soon.
Example
The example below will set the max-listener-duration on the first mount point. If there are multiple mount points then you can simply duplicate the <mount> directive for each mount point that exists.
<icecast> <mount> <max-listener-duration>43200</max-listener-duration> </mount> </icecast>