I was really disappointed it wasn't repeatable. Had I known that I wouldn't have rushed through it.
I don't risk it with GW2. They tend to make things unavailable to complete after only a couple of days of being active (I believe the fireworks achievement was one of those), so procrastinating on meta achievements is dangerous. Not to mention that they have a tendency to cut events off before the end date, such as disabling the Molten Facility on a Sunday when the event was ongoing until Tuesday (same thing happened with the Mad King's dungeon). It's just best to get things done as soon as they're made available.
Edit: Just did the new story instance. When are they going to make these new faces and hairstyles available? D: Even one of the norn NPCs has a new tattoo design.