I made one big request for change, pretty early in the relationship (one year in?). It was an ultimatum and one he knew I'd follow through on. He did. And we've been happier for it ever since.
My college boyfriend drank himself into a serious heart problem. Drinking landed him in the ER multiple times because of the heart trouble and almost killed him. It ended his first career. I will not put up with that kind of bad health decision again. Early in our relationship, DH had some hobbies which put his health at risk. I told him he had to chose between me and those hobbies. He didn't decide immediately, but it has been for the good.
Yes, you can ask for something big. But only on fair terms: do it early enough that the other person can walk away. Know what you are asking. Know if it is something they can actually change. Be okay with being turned down. Know what you can and can't compromise on. Don't ask for a change if you are okay with a compromise.
i think the fact that you were willing to leave is the key, here. you didn't say change just because. you said change because if you do not, you are not the man for me. so, he got to decide. was he the man for you or was he not? he decided that he was, and then followed through. you know?
the problem is the square peg/round hole. where you want someone to change and you think they should change and you wish they would change but they don't change and then you're miserable and they're miserable and everyone would be better off single and trolling match.com. that is something ain't nobody got time for.
Oh, absolutely. I think you ask for a big change only when the options are leave without asking versus asking. Actual follow through when he refuses is crucial. Not because you want to make a point but because you deserve to find a partner who fits.