Why do most conferences require talks to be submitted 5-6 months beforehand? 

I am primarily interested in political and technical events. Both are driven by the topic of the day. A lot can change in a couple of months. 

The only conference I've gone to for the past few years is Netroots Nation. I like the conference but am on the fence about this year. I wanted to talk about Donate Your Account but I've missed the deadline. It also wasn't clear that I could even apply to speak without some sort of nomination. 

I think people decide they are either going to go to a conference like Netroots Nation or not go. I don't think they decide based on a perfect schedule of sessions that meet their requirements. You know who is probably going to speak because they speak every year. 

My favorite events have been loosely structured and somewhat chaotic. The Tank in NYC has hosted some of the best. 

I guess what I'm saying is: Justin Krebs should run Netroots Nation :)