There is a new field added to the hardware asset form called "Eligible for refresh" from Orlando release onwards

Orlando and upwards

This field was introduced to support a new functionality in asset management, where we can know the expected life of a hardware model. Once that life has reached it's limit on a specific asset, this flag will identify the asset as eligible for refresh. 

There is a schedule job "SAM - Calculate Asset Refresh Eligibility" that runs weekly:

https://<instancename>.service-now.com/nav_to.do?uri=sysauto_script.do?sys_id=625c3df3739800109a1136366bf6a7d7 

This scheduled job calls the "process" method in "SAMRefreshEligibityCalculator" script include: 

https://<instancename>.service-now.com/nav_to.do?uri=sys_script_include.do?sys_id=ec1751fcd1510010fa9b55a1cf1df891 

Here what the script does, it fetches the hardware product model record for that asset, and looks at its "useful_life" field. Then it compares the "created on" date of the asset, and determines if the asset is still in the useful life period. In case it is not, it will mark the "Eligible for refresh" field to true.