Activate Deactivate Household Registration HHR

My wife (Taiwanese) currently lives out of Taiwan. I’ve heard of stories of HHR becoming inactive(註鎖?) in cases where a person lives outside of their registered area for long periods. I would like to find out how often she has to return to Taiwan to avoid HHR deactivation. Also, out of curiousity, how does the authorities activate & deactivate HHR?