I keep mine until they can’t be kept any longer. I’ve been known to wear “barely there” scapulars, and faceless medals.
In the event that they aren’t usable any longer. I burn them and bury them. Or, in the case of medals, I put them in a special place where I can go back to them occasionally and think of how I’ve been helped by the saint on the medal. I purge this little stash once in a long while too… just so I don’t get too attached to them.
God bless,
Agricola