I haven't read all the replies, just the 1st few and the OP.
Frankly, I found that a very condescending and pointless thing to write as however a family decide to "arrange" themselves, that's their business.
I have 2 children and there is a gap of 13.5 years between them. There was certainly no sinister motive in this great big gap and I would have love to have had a 2nd child sooner, but all sorts of circumstances prevailed which meant I couldn't.
Despite having a gap which apparently some people might find "selfish" or "indulgent" (why it should matter to anyone but the family concerned I don't know) I certainly don't fit the stereotype of the lazy mum suggested. I have only ever been a f/t SAHM for 2 years of my life, worked 9-5 the rest of the time and got a 1st class degree whilst a single mum. I am now "at home" looking after my daughter but I work full time during evenings and weekends.
Even if I had been a SAHM and then had another just as my youngest went to school I really don't see why that's anyone else's business. Noseyoldbag may still be harbouring feelings of resentment at being displaced by her younger sister, but this hardly renders every other family with similar gaps as selfish.
BTW, I'd question how many large gap babies are accidents, or unilateral decisions made by women alone. Far from being immaculate conceptions, I'd wager that the largest majority are mutually planned children, and, shock horror, there is also a man fully involved in their conception.
NOB comes across as quite a misogynist actually.