I am a FAA certificated A&P mechanic with 20+ years airline structure and avionics experience. An FCC(GROL) license offered opportunity for 6 of those years in a bench avionics shop.
All aircraft wiring and harnesses are built with properly maintained tooling using aircraft grade materials. All other wiring is built with the same tooling to rigorous aviation reliability standards.
Preventative maintenance has it's place. Performance can be adversely affected by increased resistance within corroded or damaged terminals and conductors.
Buyer Beware: Garmin does not sell their threaded backshell retainer separately. This is due to customers buying installation kits for competitor slide in replacements of Garmin units. ITT Cannon M85049/48 style backshells were designed to be attached from the outside. Garmin's threaded backshell retainer is proprietary and manufactured for Garmin connector screws to attach from inside the trays. If you buy used Garmin avionics, make sure the seller sends all associated connectors and mounting hardware.