This terminology needs improving
Retired devices should be renamed to "Infrequent Devices" and in general settings moved to section called reporting rather than agent settings and described as the "Infrequent devices threshold".
Just because a machine has not been switched on recently, does not mean it is retired! - it could be a laptop that is only used twice a year as a standby, but just should be excluded from certain patch compliance reports etc.

proper retirement of machines is a whole different feature as per https://atera.uservoice.com/forums/936306-ideas-and-feedback/suggestions/44000010-ability-to-archive-retired-devices