Unfortunately when mine arrived they were a week past their Best Before date, but I froze them immediately and have been eating them. As I have never had them before I am uncertain as to whether the flavour was affected.
I enjoy them as a change from Vogels.
I've never had this happen before, but one of my muesli packs was not sealed, and spilled within the cardboard box. Not tragic, but I did waste a couple of breakfast serviings because of it.