I'm not sure but the one-time event in WoW was a few days, wasn't it? The battle vs. the Ancient Karka was for 2/3 hours and the finale itself only once which took half an hour or so. I didn't play the whole weekend and got in this battle by accident. Didn't know about it and my friends either, none of them was as lucky as I was and I don't like the fact that they never get the chance on that experience + loot again.
As much as I hated the lag-issues, I really loved the battle. Wiping whole groups of people was something I would definitely love to see in the big metaevent-chains in the other zones. When that Karka insta-killed 20 people in the finale I really wasn't sure if we could do this... Now this was awesome