There are a lot of "experts" on these plans, so hopefully they will respond soon.
However, my short take on it is:
You probably need to switch plans when 2 things are happening simultaneously:
1). You are no longer seeing signs of progress from all your efforts.
2). You yourself can no longer handle the mental pressure and emotional stress of not LBing, seeing your Spouses continued selfish behavior, ect.,.
The plan B is necessary at this point to protect YOU (so that you don't loose whatever "love" or positive feelings you do have left).
Because lets face it, its very Difficult to do a True Plan A.
To be pleasent and considerate to someone who's hurting you.
How can it not be Hard to watch someone you love and want, rub an A in your face daily?
IMO BOTH of these factors need to be in place in order to justify switching to plan B.
Also keep in mind plan A is meant to have a time limit.
If there is NO time limit set (that YOU will stick too) then you end up just becoming an enabler. YOU DON'T want that!
So I guess there are 3 conditions:
Ask yourself,
First, are you really sticking to the "rules" for a true Plan A? (crucial to get anywhere)
Are you still seeing results from your actions?
Are you still motivated, committed, and strong enough to continue in plan A or are you getting burned out and therefore not STILL doing a real plan A?
Where are you at as far as a time limit?
Once you answer these questions for yourself, I think you'll know in which plan you need to be in right now. (And it may not be the ONE you WANT to be in).
Please don't despair, it seems that most plan A's do lead to plan B's.
The important part is doing plan A well, so that the plan B can be effective.
(plan A is kind of like the set up man in baseball)
They are interdependent upon one another and you must follow the blue print (if you wish them to succeed, i.e.,: stop A and save your M).
Hope this helps.
I would ask that others please respond as well.
Take care