there's no clear line like that. especially in someone tolerant like yourself. benzos make drinking even riskier. the compulsive nature of drinking increases while the distance between drinking and blackout behavior thins significantly. the combo is much more addictive than either substance alone. you'd have to be a heavy, heavy drinker or also using opiates before death by overdose really enters the picture. more likely death by car, water, police, heights, glass, etc. because you're out of your mind drunk.
that's in play constantly if you are a daily user. if you can't feel the benzos, they are still there ready to amplify the effects of alcohol.