I am seriously unhappy with this as much as the OP. It really does frustrate the living hell out of me. If I would have know these achievements and story missions were only available for a short period of time and then I would not be able to complete them, maybe I would have done them.
But this kind of blatant oversight on many of the older / working / parents of this community is quite sickening to me. Seems Anet doesn’t really care for those of us who have other things to do, but would rather tailor to those who can be on at least once a day at one point or another. Frankly, it’s a slap to the face. Here’s content for you to do, sorry you have a life, guess what – you can’t do that content anymore.
Pretty freaking lame if you ask me.