I had a back to metal re-spray and the only rot was around the sunroof only because I started to repair the seam seal inside the glass aperture, but me being me! didn’t finish it and the capillary action and it sitting for 7 years outside killed the roof area.

Like you I wax oiled it back in the 90’s so the seals arches & chassis rails are spot on and it’s spen it’s life out in the open, so wax oil must work if done properly.