I have worn glasses for 20-25 years; glass lenses, plastic
frames.  Every year or two I get a new pair, as my eyes
change slightly.  Usually the store technician gets the
frames fitted properly the first time, but occasionally I
have to return for a second adjustment.  No problem.

About 6 months ago I bought a new pair, and the plastic does
not seem to retain its shape.  The store technicians have no
trouble heating and bending the frames to fit my head/ears,
but after 2-3 weeks the plastic seems to have relaxed, and
requires another fitting.

Has anyone here encountered this problem?  If so, what
solution have you found?  Ideas for me to explore?

(Is there another newsgroup which might be more
appropriate?)

Thanks.