Anecdotal evidence I know, but I heard from my AS Chemistry teacher that a previous student (who went to either Oxford or Cambridge) of hers was telling her that he had a practical that lasted eight hours.
Firstly, would something like this be feasible, and if so, would it be a common occurence or just a rarity?
Not to mention, that I can't really conceive of any practical that would last such a long time. What do you guys actually do in those practicals if you don't mind me asking.