From what I've been told by parents who have done it, it takes half the time. 4 hours a day is the usual, from what they say.

I wish I had 4 completely open and free hours a day to just devote to my principles. Sadly, since I've lost the government babysitter that covered most of my work shift, I now need to work double shifts to afford a professional one as both I and my wife worked full time to afford a decent house in a neighborhood that isn't crime riddled to begin with, which means the child needs supervision for the entire now open day.

Also, you've now removed the incredibly crucial socialization bit from schooling, which means you now need to devote way more than just 4 a day to making sure they get that proper education too in other manners. One of my best friends through high school was taken out to be homeschooled and I can promise you his daily life was way more than just 4 hours, and that was a mostly grown teenager who didn't need hard structure to keep focused.

Its easy to say when you are just watching other parents do it, but none of this is just that simple. Its a great idea in theory, but well beyond the physical and literal capabilities most parents have. Which makes your "you deserve it" crowing say more negative things about you than them.