hardest thing on electrical system ?

Long ago I worked for an old man who had been working on cars since the 50's. I was daily driving a 1968 273/270 dart hardtop. we were sitting around on milk crates watching it rain as it was slow. He told me hardest thing on any car wiring is car wash soap. I questioned it and he told me best way to end up walking is wash that wiring with hot soap and water once a month at car wash. Later I thought about it and it makes sense. Been washing motors with rinse cycle every since and doing only when absolutely necessary.