Michelle & John,
I have spare sets of spark plugs for my Bonanza. At annual I swap
them out. The used plugs are sent to Aircraft Sparkplug Rebuilders in
California for overhaul. They come back looking like new, sealed, and
yellow tagged.

The cost is either $3.00 or $3.50 each. They advertise in Trade a
Plane.

I dont think that I have ever felt a missfire ot pop using this
practice.

Bob