What does it mean to "retire" a set?

Wondo

Griffins

If means you've either sold or have no intentions of working on a set anymore, and in order to keep it in the all time finest (if it's over 90%) you retire it.
Once retired you can never again add the certs to any set you own.

Wondo

Thank you

qualitycards

You don't have to official "retire" it.
As GRIFFINS stated once a set is 90% complete or higher
you can delete it and it automatically remains in the All Time Finest section
but no longer remains in the Current section...jay