In an enterprise environment you may have machines that lots of different people log into. In my case there were a few PCs, that over 300 people had logged into, in the last two years.
This caused an issue with SCCM as it gathered information out of these profiles to update the devices inventory and the MIF file size was over the maximum, so was never loaded and put into the BADMIFS folder on the SCCM server.
So to fix that you can apply a setting in a GPO
Configure the setting under Computer Configuration\Administrative Templates\System\User Profiles to be Enabled
Delete user profiles older than a specified number days on system restart to 90 days
The cleanup is done when a system reboot is executed.
You have then to be sure that the systems on which this setting is applied are frequently rebooted so that the cleanup is processed as expected.
For the example of 300 profiles – 200 of them were older than 90 days , so it can take a little while for the PC to get to the login prompt for on the first reboot.