Implement a feature where you could set criteria for machines to get automatically purged from DRE.
Criteria options you could set may include:
Machines that have not been online for X amount of days
Machines in a particular group folder in DRE i.e. Testing that will automatically get removed from DRE after X amount of days set
Machines that have been online for more than X hours
Machines with duplicate names in DRE (added multiple times without being properly removed by technicians). Let the last computer account record win and the previous computer account get purged.