When I was a young boy my father told me that a man who hits a woman is a dog, and has no honor.
I don't care what excuses people give as to why they did it, they are still dogs.

So in answer to your question, ONCE, as far as them saying they will change, in my opinion, change is something you wake up with in the morning and it leads and guides your whole day. it's not something you decide at 4:30 in the afternoon, and then say you start tomorrow.
Saying you'll change and actually changing are 2 different things entirely.