But I'm not arguing against rest per se.
I dislike England players being rested and then playing in the IPL. And I dislike all other Test series being so self-consciously seen as 'preparation for the Ashes'.
I don't care too much about the T20 World Cup.
Again, I don’t think the ‘preparation for the Ashes’ thing is as widespread as you’re suggesting and I think it’s more of a fan thing than the players (who don’t get me wrong obviously look forward to it on a personal level). The only major discussion that I remember being geared towards preparing for the Ashes is trying to develop a bowling attack that can succeed in those conditions but I think that is prudent anyway as the hit the deck quicks will be useful in almost all conditions.
If anything I think this is a legacy of not having a competition to pull Test series together so I think that team management almost had to pick an arbitrary cycle over which the team could develop and peak and due to their importance to the public Ashes series provided a logical endpoint for that. Interestingly the 2009-11 team aimed towards reaching number 1 status rather than the 2010/11 or 2013 Ashes. It will be interesting to see if this changes as the Test championship evolves.
Sorry for bringing in the football analogy by the way, unwise!