I'd have to go back and look, and maybe I typed it all out and hit the "delete" button. Which I do a lot.
Anyways, I thought I said once, I don't think time together really makes a difference. When your spouse checks out, they check out. Heck, 22 years means nothing to my wife right now (she recently said that she's regretted marrying me on our anniv. date cause it prevented her from partying with her friends, but she picked the date), and in your case almost 4. I've read 100's of posts and longer time together certainly didn't correlate to better success.
I gave it 110%, I have no regrets that I tried everything. I think one gets to the point that they eventually realize changes have to be made by both people for any chance. Some people want to change, some are almost incapable of change, and some don't see a reason to change. And some people just run.
In the end we all realize what we do for ourselves, the changes we make, the decisions we make during our journey are really the only say we have. It also teaches us a whole new level of interaction with others, on many levels. And the regrets or lack there of that we will carry with us the rest of our lives.
So what I guess im trying to say, is don't have regrets, if there is something you wish to do, DO IT. Don't want to sit around another year from now saying "I wish....", take on those demons of regrets, face them head on, but be strong enough to say you tried with no regrets. And your willing to live with the results.