124-year-old Hennessy Cognac

[Kcwhippet]

For the most part, once spirits are bottled, they don't change as long as the seal is unbroken and the bottle doesn't go through any great environmental extremes. So, if that bottle wasn't stored in the cupboard over the stove all these years or in and out of a freezer, the Cognac itself should be very close to a Hennessy Cognac that was bottled last month. All that said, your sister could well be correct.