those are not a good thing .......turn it to 100% and never touch that again
see when u turn it off 100% the bulb is not working correctly ........it needs a set power to get the gas excited to put out the right lightwaves and to full use the bulb when it is not getting that power it does damage to the bulb and it is not the correct lightwaves
a fresh out of the box bulb is about 20,000 hours of run time most shops/ cash grows only use the bulb for about 8-12000 hours then they change the bulbs out for a fresh one to get back the lumens and lightwave drift
You've got a lot of that right. HPS isn't quite as vulnerable to underdriving as MH, but it still shortens life and shifts the spectrum- which in this case makes a crummy spectrum even less desirable.
However, twelve hour days rack up the hours pretty fast; one ten week run puts 840 hours on the lamp so three cycles puts the lamp over 2000 hours, at which point most commercial operations replace them.
If you want to run HPS and not change your bulbs so much, get DE lamps and fixtures. Up front cost is a bit more, but lamps last a lot longer with less lumen loss, and they're a few points more efficient.
Or, future proof yourself now and start building DIY COB LED panels. The guys here in the RIU LED threads are some of the best at it right now, and they're already fabbing up panels that DOUBLE the PAR/W of HID lighting.
In five years, growers still using HID lighting will be considered dinosaurs.