CeMar, I was ONLY speaking from the standpoint of the kids, NOT the standpoint of a desperate and lonely and unfulfilled HD.
Caution: Opinion follows... your milage may very:
I agree with you that "the best" thing for the kids is to be in a loving family with two parents who love, respect and support one another. However, if this is not possible, then the NEXT best thing is to continue to be in a home with two parents who love and care for them, as long as the sitch between the parents is not openly hostile (yelling, constant bickering, back-biting, name-calling, etc.) or abusive (as above, but worse, and including physical agression or violence). They will be better off from almost every perspective. Economically... no contest. Emotionally, how can there be any question? Not to mention that as long as the family stays "intact", there is at least SOME hope that the sitch can be saved.
Now, in the above scenario, the person who REALLY loses out is the HD spouse. They, in effect, sacrifice at least part of their life for the good of their children. Not everyone can or should do this, but my opinion is that FAR too few people chose this route these days. People have become lazy and self-centered, for the most part. WAY too many people consider it an "easy thing" to break up a home, and leave their family, on the mere basis that they "feel unfulfilled", and "don't want to be married anymore". They have "grown apart" or they feel that their spouse is "stifling them". HOGWASH!! If they have kids, then they have a RESPONSIBILITY to those kids, to provide them with the BEST environment that they POSSIBLY can.
That said, however, I do agree with Dr. Phil that sacrificing one's WHOLE life under such circumstances is foolish and unneccessary. If a M is simply not working, and one has done EVERYTHING one can to resolve the sitch, then when the kids are old enough to handle a breakup, it is time to move on. Howver, it is definitely necessary to continue trying right up until the end, or until EVERY possible avenue has been explored.