I have just under 25k on my G8.. Mine collapsed the first year I had it causing a lot of friction underneath. This caused my white paint to discolor around my strut mounts under engine compartment. Wasn't happy but Dealer fixed the issue.
I have not had a problem until last fall. Looks like mine are collapsing again. So IMO you are better off with aftermarket ..Im now going to do my homework on the ones BLKG8 provided the link for.