There's no real limit - more a matter of behaviour. Think of it like a night club. Be absolutely bladdered but quiet and well behaved - all well. Have a few and get noisy/silly/punchy/obnoxious - expect to be thrown out. Unlike a night club it's a bit diff to throw you out once you've set off. Also unlike a night club your fellow passengers can't move to the other side of the dance floor to escape yr behaviour (and they might be nervous flyers too). So - the cabin crew have to make a judgement as you board and before the ac departs.
As said above, dry air and lower pressure don't always mix well with booze. Something else which seems obvious but can catch you out - are you getting a hire car or driving home? Sadly holiday booze will still set off the breathalyser! I have a couple of friends who cannot fly without a fair amount of sauce - they drink quietly and then behave.
hope this helps
DH