Second suspect is laser aging - but you'd think that
would affect writing only, not reading. Seem a lot
of internal DVD rewriters have still to be cleared
from decade-old inventory. Do lasers age wwhen in the
box?


Laser aging- sure. But a laser ages in a non-linear way in most cases, and also the reading process is subject to "Cliff Effect". It is fine until it isn't.
The process of burning a DVD is very slow to avoid corrupting the data. This is somewhat tolerant of a weaker laser. Reading on the other hand is much faster, and so less tolerant.
You may have a confluence of causes - weaker laser, aged DVDs conspiring together. As you suggest, it may also be a software issue, but that should be an easy and specific fix (patch).

"Aging in the box" That would depend on what elements age. Lubricants (if any) - will age. Motor bearings will age, used or not. Anyone who has worked on clocks will tell you that if a clock sits for a very long time, it should be cleaned and (VERY CAREFULLY) lubricated before re-starting. I doubt if the electronics will age in any significant way, assuming proper wrapping and storage conditions. We are long past the days when capacitors had a definite life whether in use or not. And I suspect that the same would apply to a solid-state laser.

Peter Wieck
Melrose Park, PA