My car is about 10 months old with 5300 miles. Our numbers are very similar 253-254 @90% and 282-283@100%. I balance my battery regularly and I'm curious if you do the same. Before I started doing that I was at 248 @90% and 279 @100%. Some firmware updates along the way also might have helped.
I don't, although I have range charged a number of times since taking ownership of the vehicle. I normally keep it at 90%