You're right, Diki...we aren't (or more likely, you), and thankfully for the manufacturers we aren't.

If they "froze" things the way they are, like Roland did with the G-70 and E-80, then they wouldn't make any money from TOTL arrangers, and would have to drop them from the line, and Yamaha would be in the same mess Roland is in.

Everyone has their own type of buying habits...I wouldn't have bought the S910 if it didn't have things I wanted...not necessarily needed...you tend to be more frugal, and not everyone is like you, especially when it comes to luxury items, and arranger keyboards are that for most buyers.

Plus, as I said earlier, buying amid-range is not the penalty it used to be, and it allows me to upgrade, however incrementally, if I so desire, without too much cost.

If it was a TOTL I had bought, like a G-70 or Tyros2, I'd be more likely to hang on longer.
Car makers change models incrementally every two to three years...there's a reason for that...it's called marketing, and they've been doing it for quite some time and very successfully (except for the US industry, but that's a whole different ball of wax).

Yamaha's marketing model may not be your cup of tea, but there is no denying it works...and that's the bottom line.

If they used your ideas for marketing, they'd be far less successful, but that's why you're a musician, and not into mnarketing...thanfully. ...you'd have the company in the hole in no time.

99% of "arranger" buyers consider the instrument a luxury item, not a tool for work like you.

Ian