Js, there are no rules saying that you can't end it. You can anytime you are ready. My only advice on that is to do it, not say it. Many LBSs want to sit down the WAS and have "the talk". That's the illusion of action. Words are just words.
When you are ready to end it, you go file for D and s have her served. Stop hiding the situation and let people (on your side not hers) know that you guys are getting a D. And start moving on with your life (actually you should already be done this last one!).
My sitch was relatively short. With my lack of patience I probably would have filed at about the 6 month mark. It never came to that but I'm no where as strong as others!
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018