Rotax is very well built, but if, due to the CVT, high speed cruising RPMs are 7,000 versus 4,500, the Rotax is going to turn the same total number of revolutions in 6 years as a motor turning 4500 RPMs will turn in 10 years. Or, in terms of mileage, 60,000 miles versus 100,000 miles.
As a comparison, my 2014 Honda CB1100 was only ~5,000 RPMs (~60% red-line) at 100 MPH (6th gear), whereas the Ryker is at least 7,600 RPMs.
My 2022 Triumph Street Twin, 900cc OHC, 4 valves per cylinder is 4,200 RPMs at 80 and 5,200 RPMs at 100
For legal cruising speeds, such as Interstate 15 in Utah, 75-80 MPH Ryker RPMs are 6,500-7,000.
The Ryker is a great roadster/hooligan/hot rod, but at 80 MPH, it is very high RPMs.
My 2020 did well on a 1105 mile 6 day trip, but higher RPM may be tiring for a regular long commute.
Also, 33 MPG for the 900 was disappointing.
Did not get much activity on this 600 thread
https://www.spyderlovers.com/forums/showthread.php?133902-Ryker-600-stats
I test rode a new (off the show room floor) 600 while the dealer was assembling my 900.
I did not want to push a new motor, but it did 70 on the Las Vegas 215 belt way effortlessly.
So, a top end of 90 quite likely.
The advantage of the 900 is high speed passing and pulling a 6% grade
600 or 900, it is a "great local machine" and is capable of long distances, just at higher RPMs.