You have more experience in this business. I can see how bacteria on the resin and gravel could negatively affect efficiency of the softener. Before I started reading about softener maintenance, I thought you could continue using a metered softener until the resin was saturated and could not soften anymore water. Say for example, an arbitrary softener that could soften 2000 gallons before regenerating. I thought you could use the full capacity even if took one or two months. Although it would waste less salt and water, it seems it's not a good idea for that much time to pass between regenerations. I'm guessing because of the bacteria problem for efficiency and health reasons. It seems most softeners regenerate approximately once a week or at most every 14 days. The best compromise would be to regenerate a metered softener depending on the water volume or number of days since last regen (whichever comes first) to keep it clean.
How often do you set your softeners to regenerate or is that only possible with the time clock style valves? I was hoping the electronic metered valves could do both (meter and time).