Maybe a dumb question, but why is it so important (at least according to my manual) for the upper & lower thermostats to be set to the same setting? The way mine (80 gallons) gets used most of the time (heated slowly over time by my boiler via heat exchanger), I get intermittent stratification. Which is fine - and we never run out of hot water. So I'd like to turn my bottom thermostat down some so the lower element won't come on during those times, as there is still lots of hot water in the upper part. What bad things will happen if I do that? I'm thinking that if it is so critical, they would only have one thermostat setting on them anyway since even with best eyeballing, there is bound to be some little differences between them no matter how good you try to get them the same. Plus they're not exactly the most precise control devices around.