Another new check box with the new System Center Configuration Manager release will help you massively to have a functional WSUS Infrastructure for your SCCM Environment:
If you activate this checkbox, a WSUS Server cleanup will be started after the next software update synchronization is done.
As also outlined on the TechNet Webpage, the cleanup will afterwards started every 30 days, which should be a good value, maybe we can modify this value in later versions.