imho
It would be very nice to have the deadline after some of the local events - like Hackaday supercon ( this weekend, 1st weekend of Nov. ) - where we can encourage those we meet there to post a presentation.
If we can do it even later - then we can promote the close of CFP at So Cal Code Camp LA - typically mid-November.
Closing it after either event imho would help us recruit presenters we may see at those events.
Of course, the other option is to close sooner than those events ( like we did this year ) - and allow an exception if we see some good presentations worth inviting.
Thank You