The alternator (or rotor) fails from time to time. Mine lasted 110.000 km.

I don’t agree that it’s hard to get new parts. In Africa and Asia the police and army used to drive airheads and there is tons of old bikes which are not in use and tons of spareparts. I bought a new rotor from the police in Zambia. The rotor was from an R100 but after 50.000 km it still works in my R80 (I also changed the stator).

I got my old rotor rewinded for a few dollars and brought it as a spare.

Imho the rotor often brakes because you have another fault on your chargingsystem., mine broke because the diodeboard (from Motorrad (?)) was not grounded properly.
The diodeboard is a weak part but if one diode breaks you still have 60% of the power, in this state you can go on forever but the rest of the diodes might burn if you still wear your west.

If you have a good battery and your cables are okay then most of the parts will last for a long time. It is smart to mount a volt-meter on the handlebar. If you have a voltmeter you will always know the state of your charging-system (incl battery). When my rotor broke I had seen for days that something was wrong on the volt-meter but I ignored it… If I had stopped and tightened the bolts on my diode-board the rotor would not have broken.

The charge-lamp will not lit if the rotor breaks or if one of your diodes breaks.
So with a voltmeter it’s easy….. If the voltage drops then turn off the lights and electric west and you can drive for 5-15 hours, dependent on your battery! If the voltage oscillates then find the loose connection…

When it comes to electric west I don’t see the point in using it…. My bike never starts at –20°c anyway…