Why are you wanting to use Accoya? If your making them yourself the only real cost is the material. So, IMO if they are made correctly and painted properly your looking at a life expectancy probably longer than you will be ever need. The Sapele windows in my house are now over 50 years old, needing some repair in places due to poor maintenance and also some manufacturing stuff but, not difficult repairs and only to the sashes.
If you seal the end grain in the glue joints, vent the rebates, use modern glues, paint it with say environmentally friendly linseed oil paint, I’d imagine they would still be going strong when your helping the roses grow. Looking at the prices of the Accoya you could make six windows out of Sapele for the same money as one out of Accoya (wood only). It’s a lot nicer to work with.