Joseph Meehan posted for all of us...
I don't top post - see either inline or at bottom.

Doug Kanter wrote:
...

Vibration will affect bulb life, but not the tendency of the bulb's
threads to get locked in place. And, the same thing happens with
base-up installation in things that do NOT vibrate, like certain
light fixtures.

Maybe because heat rises. Curious.


I think it's more along the lines of:
CHEAP sockets.
CHEAP bulb bases

Sockets and bulbs used to be brass now they are alumimum foillike...
--

Tekkie