My kill swtich died on me. I used the kill switch as the sole method for shutting the motor off. There was about 76k km (47k miles) on the bike at the time. It was always stored indoors but was ridden in the rain a lot. The contacts looked to be somewhat corroded. I have ridden the last year with the switch bypassed (an emergency on road repair).
My kill switch did not show any fault while starting or stoping the bike. Problems showed up suddenly one night on the highway in the form of a violent jerk due to the motor shutting off for a fraction of a second. I actually thought I was hitting pot holes on the highway (It was night and raining VERY heavy - I couldn't see the road surface well enough to tell). It was about 4 days later when when it shut off while riding. I was able to pull things apart and find the problem. Intermitant problems can be hard to diagnose.
I plan to replace the switch this winter. They do not sell just a new switch or contacts. It looks as if it comes as the entire right side assembly. BikeBandit lists it as $81.17.