Some performers can get away with a higher level of lubrication than others
That's certain. I saw Warren Zevon and his band in about 1980 at Moby
Gym in Boulder CO. The crowd had to wait in line outside for 45 minutes, and the rumor going around was that Warren was missing and couldn't be found. After we were finally admitted, he staggered out to the piano and began to talk to the audience in a completely unintelligible drunken/stoned drawl. BUT...you would never have known he was loaded from the excellent quality of his performance.