Using the silca "secret chain blend" wax and using one application of their "super secret chain wax" direct lubricant at the first signs of a squeak that indicates it is going to need rewaxing soon I average around 400km per waxing during the dry months of the year.
I just make sure I give the chain a wipe with a dry microfibre cloth every now and then to remove any dirt and it is pretty much good to go.
I have only been waxing for just over a year and I am still honing my technique, particularly in regards to the chain cleaning in between each waxing. The cleaner the chain the better the adhesion of the wax so I'm hoping to improve those numbers a little bit over time but I don't think I have too much room for improvement.
The best I have had so far was 550km on one chain waxing. The worst I had was 150km when it was very wet.