Tzippi- Duchaning by Shacharis is mentioned by the Mishna Brura as a minhag in some places. In other places duchaning is done by Mussaf, as always.
He cautions though, that the Kohanim should not be drunk.
The amount that renders a Kohain unfit to duchan is a rivi’is of wine. Other intoxicating drinks do not necessarily render a Kohain unfit. The “red line” is if the Kohain cannot speak properly before HKB”H.
The above is the din in Shulchan Aruch. Practically speaking, as others have alluded to and much has been written about lately, the best thing is for there to be no drinking at all. We have all read about teenagers who start their drinking habits on Simchas Torah or Purim. As adults, we must act responsibly and set an example for our children. Being that invariably some adults get drunk on Simchas Torah and Purim, it is essential that alcohol be banned. Hatzolah prints warnings every year on Purim about this issue due to the many severe accidents they respond to.
If ERIC55 would give this some thought, perhaps he would not think the drunks provide so much enjoyment. What they are giving is a terrible lesson to our children.