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Join Date: Sep 2012
Location: SFO
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Posts: 44,324
35 minutes before landing is fairly typical for them closing the bar.
Is the issue that they weren't offering every 20 minutes, or that they were refusing when you asked?
On my most recent flight, I went up to the galley, ordered a drink, the SD made a comment that I'd had a few, but I seemed fine, so had no issue giving me another.
They certainly aren't bringing the cart down the aisle every 20 minutes though, if that's what you expect.