NZ has the same problems with our rugby players. These days the All Blacks play pretty much year round with Super rugby, Test matches ITM cup and then end of year tours. These days the top players are taking sabbaticals (Carter, McCaw etc) for a year. And most have given up on ITM cup (Provincial rugby). If you want your best players playing test cricket then they need to have a break, simple.
As it has been mentioned on an earlier post, it seems like businessman are running the England team into the ground. I feel sorry for them, yes its their job but a person can only play and train so much before they break down physically and mentally.