Anyone who has done any level of chemistry, including home chemistry, has observed how important stirring is to dissolution. If you just dump some ingredient into a container with solvent without stirring, you're going to end up with undissolved solids on the bottom covered by a heavy super-saturated solution. Over a long enough time with changes in temperature, or heating from below causing convection, you'll eventually end up with a uniform solution. But if you need the product for some purpose, waiting an arbitrary time maybe isn't the best plan.