I am not sure if 1250 miles for a chain and cassette used a lot off road and then pounded 10 miles home mostly in eco in high gears 8/9, is bad or not. Obviously I would like it to last longer.
It is always the 12 tooth top gear and occasionally 14 tooth gear 8 that start to show signs of wear by jumping. None of the other lower gears with more teeth have given any issues so I am changing my cassette only because of a problem with the top gear.
If I wanted to go as quickly as I could all the time by using standard or high power settings I think I would then be in the 12 tooth top gear all the time and it would wear out probably very quickly.
IR772 said above that "The Bosch bikes have all the delayed start and gear changing software built in that you pay a premium for and the Kalkhoff's too.
The cheaper Yamaha is just grunt, so you need to learn to ease off on the gear changes on High, if you do not then it will crash away.
They are cheaper bikes but you need to learn how to ride them.
I have done over 800 miles and to me mine feels like new, but now I use Eco all the time."
How much of an effect not having the gear change software has is hard to tell but could be significant.
My approach has been to raise my gearing, change gear carefully and use mostly eco in the two highest gears. The gearing I now use gives me low enough gears to climb the hills I need to on my off road route in eco but I would now not want to increase my gearing further.
If you used the bike mostly on the road or in undemanding off road environments (In my opinion a great waste of the off road fun you can have with this bike) then you could simply over gear the bike to travel fast in a sprocket with more teeth, and the more teeth you have the more resistant to wear it will be and the longer it will last. Used in this way the power of the bike might well enable a rider to maintain up to 25 mph dependent on gradients but would suck a lot of power out of the battery.
I regularly commute a round trip of 26 miles now with 16 of those off road in hilly, sandy muddy Surrey before a 10 mile on road blast home with a chain and cassette still dirty from the off road trip to work.
Although now over 55 and over weight I have always enjoyed and played sport and in my teenage years was a county sprinter so my legs may still be stronger than someone else of my age and that perhaps higher power output combined with my weight and panniers is all bad for my chain and cassette.
Then again I might be deluding myself about having a higher power output than another overweight 55 year old!
I ride my bike to maintain fitness and travel cross country to work and not to go as fast as it will go and I have been really impressed that it can do this so well. I have now covered 5344 miles and the bike will be two years old towards the end of March 2017.
Oh PS my rear mech does not have a clutch!