Thank you for these guides. We have been using a Nivona type 691 since 2013. It has made well over 18.000 cups of coffee since that time (mostly crema coffee). It still works great/fine. Quality of the beans has the most impact on taste, in my experience.
It has been revised twice in those 10 years, in 2016 and in 2020 (total cost about 480 euro's), including replacement of the screen. People tend to forget these costs when they buy a full automatic machine. Also the regular cleaning takes time. Using silicon grease on the o-rings of the brew unit has made quite a difference. The insides have been much cleaner since. No more wet coffee grinds in the gears.
Not sure if I will send it out for another revision. Might try to repair it myself as a hobby project, starting with replacing the O-rings of the brew unit. I want to replace it with a real espresso machine, but my wife really appreciates the convenience of this machine.