My grandad used to use condensed milk in his tea, as he got the milk and sugar all in one go. When he died we found tin after tin of the stuff stashed in his house. Some of it even had the price stamped in "d" on the top of it... We didn't dare open it, but I suppose it still might have been edible. Of course if you boil a tin of condensed milk in a saucepan of water for a couple of hours you get quite acceptable toffee for a banoffee pie.