TeleTech wrote

What is the accepted practice relative to identifying the call area when
one has moved permanently, given that the FCC does not assign a new call
when one moves out of their area?

Whatever works for you. The FCC has implicitly acknowledged that we
are a mobile society and that we become 'attached' to our callsigns
sort of as a second name, so changing calls just because we've moved
makes no more sense than changing our name just because we've moved.
Just sign your call as issued without 'attachments'.

73, de Hans, K0HB/4ID