Jumping in late here...
As a parent of an addict I can say that although it is so difficult to stand by and watch your child destroy his life, I did have the luxury of detaching, but allowing myself back in when he chose to get help.
And as BigSis said, it comes down to how long are you willing to wait.
Had my son taken a lifetime to find recovery, my door would have still been open. I always wanted my kid in my life, the choice was his. And while I waited I could move forward in my life.
But with a spouse, an adult relationship, there comes a time that we as adults can no longer live in a life of addiction. This covers any loved one...at some point we say "no more"
But to expect the spouse to wait years until perhaps they choose recovery is unreasonable.
Although all kidding aside, there was a time I WANTED to divorce my kid.
((((Hugs))))
Cece