It is possible to keep one of these units operating for quite some time, but it requires scrupulous cleaning at approximately two to three-week intervals. I shut the unit down on the morning of the day I will do the maintenance (Sundays work well for this), and let it cool down completely (especially if it has been running at the time you turn it off).
I then take off the tank and soak it and the removable plastic screen at the bottom in vinegar (but I've also had good results with Nu-Calgon Nickel-Safe Ice Machine Cleaner - it's like CLR on steroids, and eats through calcium/lime scale from hard water like gangbusters).
I also take out the water-level sensor assembly and soak the metal tips at the ends in the same solutions. Check the ends for fine cracks in the plastic sheathing while you've got them out. If there are any, the assembly should be replaced. After this is done, I rinse them and the tank/screen in cold water. You should also rinse out the drain at the bottom of the tank, opening the lock-valve to let water flow right through it.
Finally, I get a Pyrex measuring cup from the kitchen, fill it with ice machine cleaner, and hold it up so the heating element is completely immersed in it. After a short while, the scale will be dissolved, and the element should have its normal silvery color back. Wipe the extra solution off the element. Finally, put some solution in a container large enough to dip the bottoms of the sensor wells, and let the solution dissolve the scale in them (it will drain out through the bottom holes, where you can wipe it off so cleaner doesn't drip on the floor). Allow the sensors to dry thoroughly before you re-install them, or they'll give faults when you restart the unit.
Put the whole thing back together, plug in the 120Vac again, set the humidistat for a humidity call, push the Go button, and the unit should fill and start working. As a final check, feel the front of the tank in a few minutes to make sure the element is warming up. You should be all right from this point on. Do this again in another three weeks, and you should be able to keep this unit operating for a long time.
Our city has very hard water, so I have come up with this regimen for my TrueSteam, and I've had it for four years so far. My first one needed to be replaced on warranty after a year due to the element not heating, but this second one is still working fine.