If they are raging drunk every weekend as long as I've known them, I'm going to expect them to be raging drunk every weekend until they've stopped doing that for a couple of years and I'm going to be aware that they have a fairly high likelihood of falling off the wagon if the going gets tough.
I don't think it's too big a deal if other people do that as long as they don't put other people in bad situations because of it. Generally, though, kids get put through all kinds of crap because their parents won't use a little foresight.
There were several points during my relationship with my husband where I was watching very closely to see what he would do. If he had made a deal-breaking choice, I would have ended it.
For example -- his mother was attempting to micro-manage our wedding. If he had caved into her and allowed her to do it, I probably would have called it off. I did not want a three person marriage and would rather be single than have had one.
I really, really doubt anyone (that is reasonably mature and intelligent) is going to let some little superficial thing be a deal breaker unless they have a really good reason for it, regardless of what they may think they may do.