Symbolism, Imagery, Allegory
Think of gin as a clock in this story. The story of Ed ends when the first bottle of gin reaches empty. And the story of the elderly couple at the hospital ends when the second bottle of gin is drained.
Of course, the more gin these folks drink, the drunker they get, and that helps mark the passage of time, too. But it also helps loosen them up—Mel in particular. The more gin he drinks, the more honest he is about his feelings, and the harsher he grows as well.
It's classic, really. Alcohol is a social lubricant. It makes folks say things they wouldn't ordinarily say, reveal things they wouldn't ordinarily reveal, and do things they wouldn't ordinarily do. What was that you were saying about bees, Mel?