I have Skytronic Aero-lite harnesses (plug wires) that are over 10 years old.
When I sent the mags & harness in to Aircraft Magneto Service for the 500 hour inspection/rebuild, the harness came back yet again, tested, inspected and returned to service.

I would call that satisfactory.
__________________
Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is
nothing-absolute nothing-half so much worth doing as simply messing around with
Aeroplanes
(with apologies to Ratty)
2019