I was cleaning the hall cupboard out today and found a couple of pairs of old walking boots, although they are worn and have lost their waterproof qualities I still keep them for summer walks to preserve my newer ones.
It occured to me that I am now on my 4th pair of boots since I had Ben and that I've probably had at least 1500 miles of use from each pair. On this basis I could have walked from the UK to India while walking Ben.