First, don't fall into the trap of "how long." Everyone's sitch is different.
But, my W told me she wanted a D in April 2009. We are still in the same house-sep. rooms.
A few weeks ago, W agreed to go to marriage counseling that included reconciliation as an option. Up until then, she refused any MC if it had anything to do with us getting back together.
So, it might, MIGHT, be a positive sign. But, I have no expectations (also something you have to learn), and I cannot tell you I feel any better about the prospects of our M being saved than I did before she agreed to go to MC.
If you have a LOT of time, you can click on the links to my threads below.
One of the hardest things to which I had to adjust was not viewing my W as my W. Old habits are hard to break, but you have to.