Hi!

I know the failure modes of HPS lamps (cycling, sodium loss, etc.) but I don't know how SOX lamps typically fail, since they work more like a fluorescent tube and contain lots of sodium. My only guess is eventual electrode depletion, but I don't know what that translates to in a well used or EOL SOX lamp. Suppose I have a brand new SOX lamp, run for a few hours a week, how long do you think it may last?

Electrode depletion is a possible EOL. Another failure is if the glass walls absorb too much argon, which prevents it from striking. Other times it could start "distilling", where some places of the discharge tube lose sodium and therefore get hotter, which repels more sodium away. Or they could start to leak sodium into the outer envelope. But yeah electrode depletion is probably the most common as far as I am aware.

Most SOX lamps are rated for 18,000 hours, so supposing you run it for 12 hours a day it would last over four years. I assume you are running it less than that, so probably a lot longer than 4 years. Though many different factors play into the lamp's actual lifespan, so who knows. I am sure someone else can chime in on the specifics of that.