Several things cause them to fail. Electronics, the rare metals get worn off by being cleaned with acid too much. etc.
Those are some causes of premature failure, but the rare metals wearing off the plates happens no matter how well you take care of it. That is the expendable component of an SWG, and that's what drives the ~10K hour lifespan. You cannot baby an SWG to make those metals last longer, you can only abuse it to wear them out sooner.
Marty corrects your idea about lifespan, it is generating time, but that may not be obvious how to calculate. It's
generating time, not
runtime.
An SWG does not produce chlorine in a variable way. The output setting does not vary the amount of chlorine gas coming off the plates. An SWG only makes chlorine "full blast" or not at all. The output setting is a percentage of time the plates produce per runtime. Here's what I mean:
My SWG cycles every five minutes (other brands might do this slightly differently). If my output setting is 100%, then my SWG makes chlorine (full strength) for five minutes, then repeats that during the entire runtime. But if my output setting is 50%, my SWG makes chlorine full blast for 2.5 minutes, and then it idles off (stand by) for 2.5 minutes, then repeats that every five minutes for the entire runtime. 20% setting would get me 1 minute full blast, 4 minutes of stand by, etc. So...
If you have a runtime of, say, eight hours, at a 50% setting, your SWG will turn itself on and off every X minutes, but during that eight hours it will produce chlorine for only four hours total. It's the four hours that counts against your 10K lifetime hours,
not the eight hours of runtime. Put another way, 40 hours at 100% uses up the plates the same as 80 hours at 50%. So...
If you run your SWG 24/7 at 100%, it'll last about 10K hours, or about 1.14 years. But if your pool only needs your SWG for 8 hours a day at 50% (4 hours of generating time), your SWG will last for about 6.8 years.
You can't really skimp to try and get your SWG to last longer. If you balance your water properly (we'll help you with that), you won't need to clean your SWG plates much if any at all. That's the best you can do for it. Your pool will need the chlorine it needs, determined by a dozen or more variables. You'll know how to run your SWG when you know (and we can help you with that, too). So your SWG is going to last how long it's going to last, but that might be more years than you think.