Their website says:
"All of our guests (excluding Captains) will be doing talk sessions on our B Stage, seats will be available on a first come first served basis at the event and will be free of charge. Talks will happen on Saturday and on Sunday, tickets available whilst stocks last."
There are 5 Captains and 37 additional guests. That means there should be 37 'free' talks. If each talk is 30 minutes long then it will take 18 hours and 30 minutes, not including the Captain talks. I think it is highly possible that the guests will be grouped e.g. Next Generation guests together / DS9 guests together / etc. So the talks could be finished in 2 or 3 hours.