When suspendoutput is enabled, VDR (at least a yaVDR installation) will not shutdown after MinUserInactivity minutes passed. I tried to contact the developer but he didn't answer. In the plugin's code there was a snippet that seems to do the job but it was disabled.
The attached patch enables this code and adds a menu item to activate or deactivate it. Furthermore, it corrects the indention in this section. It is written against vdr-plugin-suspendoutput-1.0.1.
This is not tested very much, but for two days until now it "works for me".