Made by a soap artisan who used quality ingredients, your newly acquired handmade soap has certainly come into your hands at a decent price. Your handmade soap does not contain synthetic detergents nor preservatives to extend their shelf life. With the proper care, a handmade cold processed soap properly formulated will last you just as long.
Here is what you should be doing:
First, if you are not ready to use it yet, store your beautiful handmade soap in a cool and dry place. Soap needs to breathe so if you need to store them avoid plastic boxes and prefer cardboard boxes or straight into a cupboard. The longer you let your handmade soap air dry the longer it will last.
Secondly, once you are using your handmade soap, make sure to keep it dry by using a water drained soap dish. That way it won't sit into a little pool of water and will last you longer.