I designed a little light sensing circuit which has been in use all these years although in the past I have made a couple of changes in the circuit due to the alarm sounding when the light was still working.
It has been 15 years and the light failed for the first time. I replace the $35 bulb with a new bulb I have on hand for next year and still it did not function. Then replaced the bulb with a known good used bulb and it still did not light.
So I ordered a new ballast for almost $70. The ballast arrives a week later and is about 1/10 the weight and 1/10 the size. (Probably an electronic ballast of which I have little regard to their life expectancy.) Also the original ballast had 3 wires and this one has 5 wires. I went on line and found out how to wire this to the fixture and sure enough it works.
What are the odds this new ballast is going to last 15 years? I am not optimistic but will sure give it a try.