999 Rear Sprocket Nuts

Are these reusable? Or a limit on the amount of times you can use? Should they have thread lock on?

 

I just found one loose, was rubbing on paddock stand while spinning wheel to oil chain. Not sure if worked loose or I didn't tighten when putting it all back together, is possible I didn't torque up when wheel was loose as hard to torque when off bike then forget to tighten when putting back together. Put some white paint pen on them so I can see easy.

 

May just thread lock them tomorrow.....