I came on site Sunday last time. I was gob smacked by how many people were already there and I was blown away how much they still had to do building wise, even the Ribbon Tower wasn't complete. All came good in the End.
It does vary from crew bar to crew bar. We turned up at the Acoustic crew bar one year before the festival got going and they were very happy to take our money. Once it started we weren't allowed in. So our cash will be going elsewhere.