Is it too much to ask for the A to stay sober forever?
It completely and utterly depends on what you want from your life. Nobody can tell you what's right or wrong here. I personally felt like my one life was too valuable to spend with someone whose addiction problems ruined my personal life, my family life, and our finances. I have friends who have made other choices and stayed with abusive addicts.
I told myself that my ex's drinking didn't affect the children. Then I spent significant time reading on the ACOA board and realized that while I thought I was handling his drinking and protecting the children, I was deceiving myself.
It's all up to you, and what you are willing to live with.