Ours is six years old next month and I'm not aware of it ever hitting the bump stops in the three years we've had it. I would say, it never has at all.
Mick, remember that Maxi has one of the early cars with the original rear beam; your car has a different rear beam and suspension setup and is less likely to hit the stops.
The original (pre-2010 model year) cars are significantly worse in this regard. I remember test driving one of the early cars in 2008 and the suspension was so harsh compared to the Mk1 Ka I was driving at the time as to be a dealbreaker.