I bought an aluminum rear sprocket... and lost the teeth around 5000 miles. It was a complete waste of money. I replaced that with a 42t steel JT sprocket.
I am not sure that this is an accurate reflection of all aluminum sprockets on the Versys. I do not know how they will age completely, but I have over 3000 miles on my alloy rear sprocket and it shows no signs of wear.
I do not know if 'Don't_Stop' is actually using a 42-tooth rear, but that is the first time I have heard of going to that small of a rear sprocket on the Versys.