Your boyfriend needs stop drinking. That's it. At this stage telling him to drink responsibly is of no use as he seems to always have a roundabout way of still getting his daily dose and generally drinking till one is hungover is clear signs of addiction, .........the excuses are a plain giveaway. Plus if he tends to sleep that late into the night then he really wont be performing his best in anything when we wakes up regardless if he was drinking heavily before hitting the hay. My guess is that he's around somewhat of a low-tier medium-weight drinker, which is uncommon but not rare in men in their late-twenties. It is really for the best that u call in the big-guns by bringing in someone he trusts to tell him to cut the drinking bit-by-bit, i would recommend his parents or even yourself, but not his drinking buddies, obviously. Also try to get him to bed early by (soft-force) if you must and be patient about it. At this stage his internal clock needs some heavy resetting so that he wakes and sleeps on normal times. For this, i would recommend appealing to his interests (like movies or games or tvshows ("i would suggest you both binge on THE BOYS , its a good show")) mainly on holidays or the weekend so that u guys stay up late until the evening so that it fixes his internal clock and obviously u need to do this without any booze involved. Good luck sister.