all toiletries have a use by, usually a symbol of a pot though with a number in which I find silly as if it says 10m on for ten months I cant remember when the hell I bought it to chuck it away, but some ingrediants in the soap may go off and give your skin an irritation
my mum used to put bars of soap in our bedroom drawers, the fancy coloured round ones we seemed to get every year ! they would be in there from one christmas to the next!! I really don;t know what happened to them as we never used them as soap! bet they are in a box somewhere with the scented drawerliners and satin padded coat hangers lol