I have attended the last 3 September pin events. The agenda was basically the same for all three. You don't have to attend all three days but - yes, you could possibly miss something. I usually leave during the day to get lunch. One of my pin friends watches my pins while I'm out. Some people come and spend all their time at the pin boards. I like to do some pin boards but spend most of my time in the back visiting/trading with my pin friends that I only see at the event.
There are pin trading boards all three days- usually a new (yet to be released in the parks) hidden mickey series is available on the boards. The back of the room is set up with tables for pin trading. They have various games on the stage where you can win some nice pin prizes. There are also various talks given by Steven Miller and the pin partners.
The pin partners have boothes that display upcoming pin releases. We usually receive a card that has to be stamped by each pin partner that we turn in to receive a pin.
On Saturday we receive our parting gifts and pick up our 4th rsp results. There is a live auction and snack time (we are given a coupon to redeem for a snack before the auction starts.) At the end of the day there are drawings for various pin prize packages, etc. You need to be present to win those or they will draw another name.
On Sunday the first few hours are for those who registered for the event. Once they open the doors for the public they change the pin boards and the new hidden mickey pins are no longer on the boards. There are many people that only come on public day and you may find some good pins in their bags.
Last year was the first time that I stayed until the end on Sunday. I made a last minute trade for one of my grail pins - the Paris pin trading night Lumpy pin. So for me it was worth staying until the end.
