Hi Phil,
As briefly touched on above, it can vary a lot depending on the load carried and, of course driving style.
I don't necessarily mean racing around vs driving Miss Daisy, more motorway stints vs navigating twisty roads.
A big factor will be whether the geometry has been well set and hasn't been altered by a knock against a kerb or through a pothole. Tyre pressure can and will have an effect too.
I would say that 15-20k is easily achieved with average use.