My folks have an old American Standard oil steam boiler that has a McDonnell Miller Series 69 low water cut-off. A few weeks ago, they came back from a weekend getaway to find that the house was 40-something degrees because the boiler had not turned on due to the low water cut-off being corroded so much that it failed. He just installed that one brand new about 4 months ago. And the one before that didn't last very long, either.

The spec page for the cut-off is here:

Does anyone have any suggestions for something more durable, or perhaps some ideas of what he possibly could be doing wrong that leads to this premature failure?

Many thanks,