FWIW, the original lower element in my 50 gal electric burned out at about the same time as the OP's, but I was surprised to find no lime buildup when I replaced it. The replacement lasted about 10 years, and when I replaced it, the tank had lime at least up to the element. I cleaned out what I could and replaced the element and it is still working after 2-3 years. I would have probably just replaced the heater then, but my truck was in the shop, and it was somewhat easier to transport an element than a w/h in a Ford Aspire. As to the OP's question about the temperature, dunno if the lower temp actually causes less lime buildup, but the fact that it is on for less time with the lower temp may be more of a factor that the second element has lasted, besides that the replacement was possibly of higher quality than the original. Larry