How long does a UTH last?

Generally, how long can I expect my UTH to last? I have a Zoomed UTH for a 20 gallon.

Mine has lasted 3 years and still going strong.

One of my Exo-Terras is still cooking after 15 months. The rest of mine are not as old...

I have a few two year old UTHs that are still running strong. I would assume they should last a good while if taken care of properly. Perhaps about 5 years? Maybe longer?

have 6 and 5 been running for 5 years and still going strong the 6th one burned a hole through itself and had almost 1/2'' space between enclosure and heat pad it was 3 years . hole is about the size of a marble so dont know what happend but they are all zoo meds and i like them alot

they seem to have a pretty good lifespan, i wonder if proportional thermostats are better for them. im using the reptitemp 500 so mine are ON and OFF constantly. im sure that takes some out of them.

From what I hear, and depending on quality anywhere from 3-8 years.
I don't know first hand, I use heat tape.