In more than 3 decades of performing on stage with an arranger keyboard, most Yamaha, I have never experienced a single, complete keyboard failure - NEVER!
Like Kaarlo, I also owned a PSR-5700, which was a true beast. It tipped the scales at 51 pounds, had great piano and vibes sounds, but only about 35 style files. That keyboard is still in use today, being played by a friend in Baltimore's Little Italy 6 nights a week, 4 hours a night. It continues to just keep on keeping on.
Mass produced electronic equipment no longer undergoes bench testing before being sent out. This is because the failure rate is incredibly small, despite what some tend to believe. It is reportedly less than 1/10th of 1 percent. The cost of bench testing each piece of electronic gear is insanely high and time consuming, thus the practice was eliminated.
As for the display on the PSR-S900, even after the warranty expired, Yamaha stepped up to the plate and replaced them at no cost. Not many companies would even consider doing this, but I know of at least two entertainers that had a problem with their Bose sound systems and both were replaced at no charge after the warranty expired.
Now, Kaarlo sincerely believes that the Genos is not an acceptable keyboard for on stage performers - to this I disagree. Admittedly, I only played the Genos for a period of 2 hours, but during that time, I was able to smoothly transition from one song to another without any dead time at all. I had no trouble finding my way through the menus and doing other things on the fly. The operating system, to me, was very easy to work with and it was my first experience with a touch screen arranger keyboard. The touch screen performed about the same as the touch screen on my cellular telephone, no hard or multiple pushes to get something to work. I was enthralled by the wonderful sounds produced by the keyboard and many of the new and old styles sounded fantastic. The store manager wanted to know if I would be interested in working there demoing arranger keyboards 3 nights a week. I turned him down for two reasons, my health problems, and it was a 3 hour drive to get there.
Over the years, I have repaired many, many arranger keyboards for friends who are pro entertainers. In most instances, the failures of those keyboards were 99-percent user induced. Some were ex-piano and accordion players, folks who tended to pound on those keys as if they had some sort of grudge against them. This destroyed the keypads in no time at all.
A couple guys had drinks spilled into their keyboards, which produced a sticky mess on the printed circuit boards. In some instances, I was able to just rinse the board with warm, fresh water, then dry it with a hair dryer and everything worked just fine. However, there were a few that I had to replace the sticky boards with new ones. One player, who was an excellent player and his wife was a fantastic jazz singer, destroyed arranger keyboards so fast that if he owned a keyboard for three months, if you saw it, you would think it was decades old. All kinds of dings, scratches and destroyed buttons. He used his thumb to mash down the buttons on the keyboard after they failed to respond to punches with his index finger. I ran into a lot of players who abused their keyboards during my 30 years on stage playing one. My keyboards looked as good the day I sold them as the day they came out of the box when they were brand new.
Bottom line, the longevity of your keyboard is totally up to the user. Take good care of it and it will likely outlive the owner.
Gary