Over the past couple of years I have been going through the process of cleaning up and restoring my large collection of vintage Lego sets from my childhood. Most of these had been stored in my parents attic for 20 years or more in their original boxes. Apart from being dusty and grimey they are all in tip top condition and I've been able to clean them up to a very good standard. Recently though my in laws were had been clearing out their house and gave me a copy of Black Seas Barracuda which used to belong to my wife when she was a child. This had been stored in it's original box with all the parts sorted in to plastic bags, the kind of bags you'd use to store food in the refrigerator. It had been left on top of a wardrobe in their spare bedroom for many years without being moved. The temperature would be pretty constant in this room without any excessive humidity. The set looked in great condition. The sails were all perfect and hardly any dirt on any of the bricks. When I began to build the set recently though a problem became immediately apparent. Almost all of the flag pieces had gone brittle and the clips snapped off as soon as tried to put them together. Has anyone else ever experienced this or got any ideas why it would have happened? I've never seen it with my old sets which had been stored in a cold dusty loft for 20 plus years, but my wife's set which had apparently been kept in a much better condition was the only one which has deteriorated.   I've since replaced all the broken parts but I just wondered if anyone can offer any tips or advice to prevent the pieces from going like this again.