Well, I am half/half on that subject. I fully agree with Quizzical, that is actually a point I had made a while back.
But I also support the "once a year" or "exclusive" events. Adding a new fun factor into the game, it is something that gives players something new and it ups the game-play "morale" a bit. While not all people at all times can always join in on those events whenever they pop up, I think that it is something enjoyable that should be made a very traditional thing to do.
As far as I know, Felix Navidad and Halloween will be back with the same outfits and pets next year, if anyone missed out on that. The same with all the other seasonal events and perks.