I planned on going back to work when DD was 6 weeks. I have been lucky enough that DF got a job that pays more than enough for me to stay at home.
I now have ds who is just 1 and pregnant with number 3.
It is financially better for us if I stay at home until they are all in school. Even then I will working from home with my own business so I can do school pick up/drop off, assemblies, home work, house work, cooking etc.