In patch 3.1, flask effects will be lowered from 2 hours to 1 hour. To balance this, flask recipes will be changed to make 2 instead of 1 adding up to essentially the same thing. This is actually a great change if you think about it since it’s going to allow for better flexibility in the usage of flasks. For shorter raids like Obsidian Sanctum, you can just down a flask for the whole run and that’s it. Even for longer runs, this change reduces the chance that you’ll finish with still a long way to go before your flask effect wears off and basically wasting the effect on more trivial purposes. maybe this change could also encourage players to use flasks even in heroics. They’re also increasing the stack size to 20 to allow people to carry more flasks.
All won’t be lost for people who stockpiled flasks. Because they essentially would have been screwed because their flasks only work for half the duration, Blizzard will allow them to exchange any Northrend flask for 2 of the shorter duration ones. So no one really loses anything with this change but everyone gains more flexibility in using flasks!