15 years of serice from an inkjet printer is outstanding: I think you should be schooling us, not the other way around
Although not exactly the info you requested, my older Canon Pixma Pro-10 (2 years?) continues to amaze me, because to date, I've never had to manually run any sort of de-clogging procedure. Once, after a lengthy idle period, I got a faulty print and realized - it was actually out of ink! Popped in a new cart, and after a pause during which the printer automatically does whatever it does, normal printing resumed. I've never known this lack of drama with HP or Epson printers.
Also, Canon does not leave "pizza wheel" indentations on the paper, and the sheen of my glossy prints is uniform, without a hint of oily or metallic sheen.