From my onw experience I can say that no mtater how much your'e drunk, only the first meters are dfficult. Once you walk, if nothing gets on your way you nca walk miles.
the best Ive done was last yuear in Pamplona ... at some point in the night I lost everybody and I went ahead in the feria and drank with other pepole, until the point where I ran out of cash, and since I was pretty wasted already I decided to quit and walk to the tent... goddamn, I could not find my way back to the camping... had to wakl until sunrise, and even after..only after the runnig of the bulls I met some dude from the camping and we eventually found our way back. I swear I walked 20 km that night. In a town that's barely 2 km wide. Dont laugh