Typical burn-out situation would have been that of riding downhill. That occurred, in particular, early on when halogens were introduced and the problem was not yet caught - regular incandescents were much more resilient with that respect. Subsequent halogen lamps both had the optics tailored to halogen bulbs and carried protectors. Still, though, the issue remained of the following avalanche effect. If the front bulb burnt out due to life, the load increased on the protector. Most could not withstand more than few minutes of increased load. After or even before the protector burnt out, the rear bulb would go. The rider would eventually change both bulbs, but now would be left without a protection.

Depending on details of wiring the rear LED light can be still vulnerable if the front light ceased to take power for whatever reason. Typical rear light lacks an overvoltage protection.