What’s the likelihood that my boyfriend will remain sober after his 10th attempt at a rehabilitation center?

My boyfriend has been an alcoholic since the age of 18 to now 27. Whiskey is his poison, and during benders, he’ll drink a handle plus some every day for days- weeks straight. The longest he’s been consecutively sober in those years is 4 months after attending a 30 day rehab. He’s now at a 6 month long program. He’s been there for two months now, and is still showing signs of relapse. I know it’s still early and I’m trying my best to remain hopeful, but what are the chances?
What’s the likelihood that my boyfriend will remain sober after his 10th attempt at a rehabilitation center?
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