I found this quote on the internet in response to the number of comments people made about being like me and not knowing what the phrase is supposed to be:
Allan Hazlett writes:
"I was one of the few who, upon learning (fairly late in life, I recall) that “for all intensive purposes” is a malapropism, was not embarrassed that I had spent to many years not saying “for all intents and purposes,” but rather lamented the fact that “for all intensive purposes” was not an expression in English. It seemed so well to capture what I meant when I uttered it - when we consider only those purposes that are intensive, that’s the sense in which this is a good idea. It’s a good idea for all intensive purposes, but not for some of your other purposes that aren’t so intensive."
I am not alone, and that feels good!