Excellent service life
Have just replaced element after 11 years. Tank still seems ok, should see another year or two. I’ve seen a number of reviews bagging Dux here. My experience is the opposite having only got 3 to 5 years out of other brands previously used but a very long life out of Dux. I’ve also seen at least a couple of reviews complaining about faulty relief or other valves. News flash to those people - blame whoever installed the system. External components do not come with the product so your plumber probably just used the valves, piping and pressure regulator from your old hot water service.