[CMcAllister]

I have one of the older chrome MSD lights, same as the old Sears Penskes, and it still works great. Has to be 40 years old. Very bright. But it's not used everyday.

I would think the amount of use would be more relevant than age. Plenty of those old lights on ebay all the time. Even an NOS MSD light on there recently. Even the old Ferrets on there sometimes,

To answer the question, I've never seen a 12V timing light get dim as it ages. If they fail, they just wont work.