Guild Wars 2

Was there any notification that this one was going to last for 2 weeks unlike all the previous ones that were available for 4 weeks? Was expecting them to be available for a couple more weeks.

There’s never really a guaranteed time that they last. There have been other releases where the achievements were only available until the next release as well. You should always operate under the assumption that the achievements are only available until the next release, even if that isn’t always the case.

Operate under the assumption that you only have 2 weeks.
The previous ones were available for 4 weeks because of the christmas break and presumably because Anet was busy sorting out the final two arcs and also getting ready for the China release.

Living stories in the past have overlapped so you had 4 weeks to get anything. Eh whatever. I’l just finish them in the first week from now on so I don’t have to worry about it

For any achievements under the Living Story category:

As FlamingFoxx said, always operate under the assumption that you only have two weeks. Generally for events that last for longer than that (e.g. Wintersday, WvW Season 1) you can assume that the achievements will hang around for longer, but even so, if you’re an achievement hunter like me, I strongly urge you to get into the habit of completing all the achievements within 2 weeks.

For any achievements NOT under the Living Story category:

This you can safely assume will be around forever. This includes stuff like the Triple Trouble, Edge of the Mists (non-LS) and Fractured.