UV Sterilizer Install Questions

[BeanAnimal]

Ive been using rainbow lifeguard for a couple of decades and last 9 years AquaUV and got at least 8-9 months out of each bulb. Lamp life is based on hours and I dont see how start/stop would reduce the life of a bulb that works part time

They are fluorescent tubes. Starting voltage and current is much higher than steady state voltage and is hard on the cathode filaments. Each start hammers the cathodes with thermal shock and sputtering (literal ejection of material) that degrades them. The old rule of thumb was 3 hours of lost lamp life for each start.