UV water purification light ballast failure

When I applied for a building permit for our garage in about 1998 the county directed me to certify my well and add to my 1969 septic system. During the well certification they required among other things a water treatment. Adding a chlorine system was suggested but we opted for a UV light purification system thinking it kills any possible bugs and does not ruin the taste of the water plus other advantages. So after quite a pile of paperwork the system was approved by the county. With the approval came a requirement that an alarm be installed if the light failed.

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.