Your wife's MLC may have begun in 2004, but I think she was in the "leading up phase" and not the actual crisis itself. They spend a few years thinking about it, or should I say, they begin to doubt themselves, they become disenchanted w/life and then something will set the trigger in motion. Your wife's crisis mostly like took off in the last 18 months. What happened in her life?
If you can sit patiently, detach and go on w/your life, so be it. However, I also want to say this, there is no way to guarantee that she'll come out of this and want to come home or that you'll want her after the dust has settled many months/years from now. Do not sit and wait on her, i.e., live your life to the fullest and leave the door ajar.
Sometimes the path is chosen for us and other times, well, we have to make the decision and move forward. I can attest to this, if you do divorce, the madness will not end with the signing of the divorce decree. Your wife will still be a part of the parenting process and she will not snap out of it. Yes, you will be able to move on and hopefully detach from her drama, but it's difficult, especially w/children in the picture.
All that I am asking of you is this...weigh the pros and cons of a divorce, consider your finances and assets and go from there. Take what we suggest with a grain of salt, sift through the advice and do what is best for you and your chidlren.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.