I was recently gifted with a 1966 Château Pavie Decesse Grand Cru Classe St. Emilion and wondered how long I should allow it to breathe after opening? I am getting conflicting info: from 2-24 hours.

Forget simple breathing.
I would advise decanting it a couple of hours before drinking.
This way you can asses it's drinkability and ensure you don't have any sediment left in the wine.

Should be drinking well, assuming it has been stored correctly.

Thank you... do want a report back? :-)

We would love a report back. How did it go? Was decanting better? At what time after decanting did it taste best?

Thanks.