My partner & I used to be physically abusive

We used to drink and get into physical fights. We broke up due to that, and we ended up getting back together and agreeing to never get physical again. It has been three years since we agreed and have not gotten physical. So my question would be do you think he will do it again in the future? Or can people really change? From what I can see we have changed. Also, I stopped drinking since we agreed, but he hasn’t. So I can majorly attribute the no drinking to the no fighting anymore (physically). We don’t have kids and we are In our late 20’s now)