It could be down to filming, or just that Brazil, with fanatical fans, has been missed out since 360 and the band have wanted to make it up.
But I've just been reading about birth traditions in Brazil (in an attempt to see if there is any other reasoning as to why Brazil gets 4 nights).
And guess what I found, now that there is a half-Brazilian new arrival in the camp -
In Brazil it's customary for all the relatives to come round and for the parents to receive visitors and then to give presents out.
Well there's 4 nights for 'visitors' to come along and 4 performances in return. That's one big party to celebrate, who says being a U2 fan isn't like an extended family?