I think one day is ok to be honest.

The problem is, so many people start leaving about 2.30/3pm, that by the time you get to certain parts of the show, half of the stands are empty!

They all leave thinking they're going to beat the queues but end up queueing anyway.

I was there til about six this year, just chatting and stuff, might as well get your money's worth. I went over the bridge this year at about 3.30 and it was more than half empty, so barely saw any of it