There are reasons in my own case why we need to help the DC, linked to their disability. My friends with NT kids are less concerned to do this.
I still think its a valid thing to plan around, though. Of course, in theory, it is our DC's own problem when they are grown up. Except we all know that the price of housing being what it is, it's a mountain to climb. If you imagine your DC aged rising 40, still renting and you are not able to help out, it would be very frustrating to be at home, kids grown up and not needing you any more day to day, and unable to get paid work. Whereas if we go back to paid work when they are fairly grown up, at secondary school, there are 20 years for us to earn and save so we can help them.
And the same is true of pensions. Pensions are crap and getting worse. And we are all living longer. It's a big load to place on DH, building up enough pension. Every year that we work, even if it's for barely break-even, is still a year in the pension pot. Obviously not for state pension, because while you get child benefit you get home responsbilities protection anyway so it makes no difference whether you earn or not, but in a private pot.
When they are little, I am sure that a happy childhood outweighs these considerations. As they grow, I think the balance shifts a bit. Well, it did for me, anyway. I only have one left in school now, and he is in his final year, and so I am glad that I have my career.