In the early days some racers had problems with the oe rear axle and nut. The nut uses a mechanical lock mechanism (don't ask me to explain how as I don't know, someone feel free to enlighten). Anyway, after lots and lots of use the reports were that the nut eventually loses its ability to perform. Bearing in mind these were racers changing tyres constantly I don't think there is anything to worry about. And it was back in gen 1 days.
Yea I wouldn't worry about the axle nut at all, I've done "high" mileage with my 15 RR and had loads of tyre changes with absolutely no issues in this respect whatsoever