If you look at any awards ceremony that takes place at a convention, I think you will find few, if any, that occur on the last day of the convention. Why? People leave early. Sunday night most people are wll on their way home. When people leave, you have no audience. I doubt people will stick around just to see the awards presented. Having the awards the night before the biggest day of the convention (Saturday) allows for the winners to take advantage of the publicity. What good would it do to win the award on Sunday night? No promotion at the convention, no discussion by fans the next day, no way to capitalize on the win. Just for comparison, the Hugo Awards are the centerpiece of the World Science Fiction Convention. they are handed out on Friday night, and have always been handed out on the Friday of the convention. Friday is the biggest night, and Sturday is the biggest day. Thats when the people are there, thats when you give out the awards if you want to have any draw for an audience.