I'm using avent steriliser. it stays up to 6hrs as stated. if I'm going to be out the whole day, how? I can bring out sterilised bottles but I'm staying out more than 8hrs. how?

Actually you don't have to worry about those sterilized bottles. They will be fine. Been using for all my 4 kids and they are going up healthily. Just cover it and it show work out well. Don't be too paranoid about it.