Jeff,
There are usually some that go over early or later due to work-week conflicts as well. Every year is different. As for me, I won't know for sure the dates I'll attend until it's a few weeks away, I hope to do the whole thing. They/we go over on Sunday or Monday to avoid the crowds on weekends (Fri, Sat), works great for groups of boats (10+), also allows us to select spots where we're all together for socializing day and night. We always have a great time. Try to get there for at least a day or two, you won't be disappointed, I promise!