I would have to agree with the "luck" theory, Lyssa. I've had multiples many, many times without baby boost and don't see any relation between it and multiples at all. In fact, when I created this thread, the only time I ever gave baby boost was if they had fertility problems. I never repeated a dose until I got the information that's posted here. Now, if I have one of those "incompatible" couples that fails and fails at having a child, I use multi-dosing because my thinking is that a small increase in chance is better than no increase at all.
I'm still documenting all doses and all multiples though. One day... maybe... I'll compile it all into stats. heh