Hmmm... haven't played much with electronic ignition (not a fan of modern day black boxes

). From what I understand, the "open points" voltage in the electronic ignition replacement kits is controlled so as to avoid any arcing at all. Crow make a point of this in their advertising (controlled by a "chip"... very 80's

), whilst Petronix make a point of telling you to pull out the condenser (then keep it as a spare just in case... those guys think like I do, and probably have a similar garage stacked with crap they cant find

).
There is not much arcing at the rotor normally, though the carbon button in the top of the rotor sometimes gets a workout. The button is spring loaded, and tends to get a little sticky over a few decades

. The button then doesn't contact the rotor very well, and starts to arc. You see crap on the top of the rotor, and the carbon end starts looking porous.
Rotors are normally fairly robust. As long as they don't chew out the locating tang, they last a fair while and take some abuse (once drove 400-odd km from Sydney to Tamworth with a rotor button held together with duct tape

).
Cheers,
Harv.
327 Chev EK wagon, original EK ute for Number 1 Daughter, an FB sedan meth monster project and a BB/MD grey motored FED.