They may be temporary due to the fact that those temp stats items are too good and that serious event fanatics will farm these items to overpower themselves and further the gap between the casual and the hardcore players. that is my $0.02 and i wonder if anyone out there shares this opinion.
@azureduran: i do not agree man. Everybody can get the event stuff. Its not that hard (even i can get them ! that says enough).
Maybe nexon does it to keep player hungry. When the temporary stats off an equip are gone you have to get something new, to keep your stats at level.