Panda - I have often wondered about my timeline as well, for the same reasons.
But I think the confusion comes because of how verbal our spouses are, or not. Some are a complete closed book until BD, and some, like our H's gave many clues as to the mess in their heads.
In the couple of years before BD, I definitely felt my H distancing himself emotionally - he said a few strange things such as 'if you died I probably wouldn't miss you', he travelled as much as he could for work to escape family life, he stopped doing things with the boys in the last 6 months, he was irritable and argumentative. There was no reasoning with him.
Sept 2009 he robotically said that he no longer missed the boys and I when he travelled for work. He was emotionally completely 'gone' at that point.
But from what I understand, BD is when they see no other way but to escape the relationship.
BD for me was Feb 2010 when he announced that we had a bad marriage and that he was leaving.
OW was definitely on the scene at this point - he was obsessed with her, but he didn't move out until June 2010.
So for you too - I think BD would be when he makes the decision to make a total break from you in Feb '13. Despite the trail of clues he gave you prior to that.