Three years, minimum. Why? Because if you want your SAHM to be able to give you a clean house, more than one hot meal a day and also do childcare with no breaks, spacing any more closely makes the former impossible. People will rebut that it is possible because they do it, but I have found that is spectacular lies. They either hide/downplay/lie about having household help (an aunt coming over every other day for three or four hours at a time somehow isn’t “household help”, for example) or they are not doing something on that list above. Cold meals as a norm is a great example, as are tips on how to hide the unwashed dishes and general filthiness of your house. Weirdly like SJWs, women who want to argue about this stuff routinely fail one of the items on the list and claim otherwise. Another fun rebuttal to the notion that child spacing greatly affects housewife effectiveness in a society where she can’t expect assistance are people who have wide spacing and then claim that it doesn’t really matter, they would have done as fine with closer spacing. LOLWUT is all one can say to that.
A lot of women find out the hard way that it takes three years or more between each child to really develop effective routine and structure (not to mention toilet training issues, children are in diapers/pullups longer these days for many reasons, and this is among them), by having 2-4 kids one or two years apart and being unable to escape survival mode for about a decade. Yes, a whole ten years. And during that time, kids aren’t taught chores, because there is no structure that would allow for it. So by the time the average Christian conservative SAHM comes out of the muck of childbearing and household chores, she generally keeps plugging away without involving the children because now she can set up a system and just make everyone follow those rules. This leads to the sad spectacle of teenagers who don’t even fix their own sandwiches, but are being raised with the idea that they’ll be able to easily adopt American Christian conservative-traditional sex roles after marriage.
Women who happen for various reasons to have wider spacing naturally find these obstacles to be smaller.