When the only acceptable method for fulfilling that need requires or results in the pain of your spouse.

MB is an intertwined program that works when all elements in place, this is why it is tricky and difficult at the beginning. It's like watching a quickly turning merry go round and trying to time the best way to get on, at some point you just gotta jump on and hope you don't fall off.

Ideally two spouses care about one another and the thought of hurting each other seems unfathomable, and thus the actions that one spouse requires of the other will not put them in pain or hurt them in any way. There is a little bit of the Giver involved where each spouse does their best and the other cuts a bit of slack until positive, need filling habits are established.

Good example is my husband's need for Affection. He likes cuddles and hugs. Me, I have an aversion to touch that was VERY strong when we first married. I would try and try to snuggle and I'd get anxious and ansy and start poking and tickling him. It drove him crazy and me trying to snuggle drove me crazy.

Now he could have used LBs to get me to lay still and meet his needs: SDs (Just lay quietly for crying out loud!), AOs (YOU NEVER GIVE ME ANY AFFECTION!) and DJs (What kind of woman are you? All women like to cuddle!). At that point, his need would have become an LB.

But since we were in love and had our Givers at the table, I would snuggle him as often as I could for as long as I could stand it and he'd lay with me and enjoy what little I could give at the time, and over time I've become more accustomed to it and am now able to provide the amount of affection he needs, because I've built the habit.

Now if you have two spouses in conflict or withdrawal it will be more difficult to create the atmosphere necessary for a successful negotiation. This is why the first step is to create romantic love by meeting the needs you CAN meet, in order to create the love necessary to negotiate the needs that are more difficult to meet and require negotiation.

Ideally you can meet other needs and table the one that is an issue and still achieve the Romantic Love threshold at which point a safe negotiation guided by the Policy of Joint Agreement is more likely to be successful - because you are working with two people in love and so they DESIRE to meet one another's needs and are ADVERSE to hurting the one they love.

Like the merry-go round, it's easiest for both spouses to get on at the start of the ride, before things start moving. Similarly it is easiest to implement MB early in a marriage when both spouses are riding the high of their first love. It is possible to do it later, but like jumping on the merry-go round spinning ever faster - it is scarier and you stand a good chance of getting knocked on your behind a few times before you actually make it on, and then once you're there you gotta stick out your hand and try to get your spouse on as well.