I first off apoligize if this is a stupid question so with that said, I am beginning to aquire several soaps and creams and am curious if there is some type of shelf life for them, what I've been doing is using one for a day or so and then switch to another but at the rate I am going wearing these soaps down which is hardly at all is going to take a long time and I really load a brush so once one starts using is there a time it has to be used within ?