Is it common for experienced astronomers to change out their perfectly
good "stock" mirrors with "after-market" mirrors strictly for higher
performance? Jan states "top quality... exquisite mirrors." Are
Spooner mirrors better than stock mirrors or just good substitutes when
replacements are necessary; as was her situation?

Almost certainly better, but would you know the difference? Maybe you
would, or would at some point in the future, and maybe you woudn't. Maybe
you don't care and just want something of high quality because you like high
quality stuff.

Anyway, tonight is looking pretty good (finally), and my sons and a couple
of friends and I are going to do a bit of observing and not worry about
equipment.

Dennis