Sounds a bit extreme, my standard GS, has EXP's on from new and I replaced rear at around 5-6k, but front still going after 9k although due for replacement a bit squared and some smalls cracks in rubber, but still legal.
But likely to depend on riding style and conditions, I do a lot of long distance commuting (with significant motorway stretches) and often in wet conditions.
With my last bike I would go through two rears for one front, although looks like I will need to change front on the GS before the 2nd rear is shot. I'm thinking of trying Tourance Next's this time!