I feel there are two steps for an LBS in ending the relationship and moving on.
Step 1- Accepting that the old marriage is over. Even if there is a reconciling, the marriage of old is dead. That is why I like the approach over here in MLC. By focusing on yourself, as opposed to forcing or controlling the overall situation, the issues that the LBS finds within themselves have been addressed. More so....those issues have been wiped out by consistency and habit. So in the new marriage or future relationships those old issues don't reappear. You have time to take ownership in the parts of the marriage that you might have been lacking instead of just saying it was all the WAS.
Down the road from that is;
Step 2- At this point you can make serious decisions about any future with the WAS. These decisions are based on a sound emotional footing. You can really ask yourself "Was the marriage that good?" or "Was my spouse really that good for me?", and of course "Will my future be better by completely letting it go?".
So I agree, there definitely is a point of no return. The issue is that a lot of people want to skip step 1. Blame everything on the WAS and take little or no ownership for their part of the marriage demise. I don't just mean lip service either...I mean real deep soul searching on one's part in the relationship. So without that soul searching they bring their past issues into the next relationship.