The event should at least be available to March 10th 2012. Because that will go thought the first year anniversary of Pokemon Black and White Versions in the US, Europe, and Australia.
If I am not mistaken Electro Ball works best on Heavier foes right? Since Wailord is heavier than Mewtwo it should do a lot of damage and same with Snorlax and the other heavy foes. There are a lot of heavy Pokemon now so if you think about it Electro Ball can be a good move if used Wisely XD.
And since under average conditions Electro Ball will rarely hit for more than 80 BP, Thunderbolt is a superior option in every case...even on the speed demon Electrode.