Thats like saying don't cosplay something that isn't popular.
How many series are still running when you go to your con. Are you making your cosplay in a week or something? for me technically it's not Ended here[in the USA] because it never even started so everything is fair game.
some times that older anime cosplay will make someones day :3
... And to answer that question "Yes I live here and have nothing better to do "
Next Convention: Otakon