i only do 8 miles a day as i live close to work.
F**king roads and pot holes do my nut in!!! 
I would write them an email, as long as there is still decent tread left they should be under some sort of warranty (if they say no, just quote consumer law, if you buy a product it should be expected to last for a reasonable amount of time etc etc.)
I got a new heated seat element and new seat cover from VW for FREE!! just because i complained and said i could have crashed! (10 year old car mind!!) You could say it could have poped while your were tankin it down the motorway!