This is just an observation. 

The house we are living in was my parents house. My dad had to replace water heaters multiple times over the years, seems like every few years. Had a lot of trouble with them. We were on shallow well water at the time. The problem was always the tank would start leaking.

When we remodeled the house we did two things different. First we went with rural water which is obviously from a different deep water well. The other thing is we put in a whole house filter. We did have to replace one water heater after about five years but it was an original that dad had put in and was not too many years old. The other water heater (we have two) was put in new at time of remodel which was probably about a dozen years ago with no problems, knock on wood.

My point is, either the water source or the filter or both had a lot to do with length of life of the electric water heaters. We have not had a problem where dad had regular problems. The only thing I can think of the filter would help is keep sediment from building up in the bottom of the tank, which would cause an element problem not a leak problem. Surprising how much crap comes through rural water lines.