I have my current espresso machine for about 6 years, never clean the water reservoir nor the machine, I only clean the coffee basket once every 3-4 weeks in the dish washer. But I do clean the steam wand every day by immerse it in a cup of water and let the steam run for several seconds. I use the espresso machine about once a day, so the total uses is more than 2,000 times already and it's still running strong.
By the way, I only use RO water in the espresso machine.