So far the game itself has been great. Its a homebrewed pun not intended 2nd edition Ad&d. At the beginning the GM was getting tipsy by the end of the game session and all was well. Now he is nearly blind drunk.
I would be concerned about this, the fact that the amount of drinking is changing. Like, if it was constant throughout your tenure so far, then you could just chalk it up to that's how the group operates.
Alternatively it's possible that this is the normal, and they were drinking less because you were new, and this is a sign that they've grown more comfortable with you.
If one of the group is a close friend of the DM, maybe you could ask them if this is normal.