The heaters usually are run 12 to 16 hours per day. The heaters are made so they have low watt density, but nonetheless, most of the heaters last only a few weeks. I am at a loss as to why they do not last.
Spots form on the heater, and they get bigger over time.
Eventually, the heater cracks. Several key pieces of information are missing. Tubular heaters generally are more durable than cartridge heaters. One cannot calculate the watt density without knowing this, and hence one cannot verify whether the reader's low watt density claim is correct. However, one can upgrade to an Incoloy or Monel sheath for increased corrosion resistance.