Many good things at SPAH. One is the Filisko Teach In.
Various top notch players, many are professional musicians, sit at small tables with half a dozen chairs around them and you just wander up, take a seat, and talk and learn from the best. You can spend an hour at one table or wander around. You can ask questions or just listen to the conversation and playing going on.
The seminars are fantastic. Again, top notch players of many different styles give instruction and demonstrations in a room of maybe 30 people.
The 4 or 5 times I went to SPAH I didn't play much. Mostly I keep my harp case closed and my ears open. So much to learn.
I also take some cash to buy a harp. Vendors often have good deals at SPAH.
Much of my harmonica music collection was acquired at SPAH. Take some cash to buy CDs from the pro players. (I guess CDs are still sold. Maybe streaming has replaced physical copies?) I have hard to get albums that were purchased directly from the artist (some even autographed).