If you notice the scent of your soap fading, try using it as soon as possible to enjoy the fragrance. Handmade soap typically has a shelf life of up to 50 years but as time passes the scent will fade so it's best to use your soaps as soon as possible. The scent will brighten up when you get it wet.  I found a 20 yr old bar in a dresser, the scent was very slight.  But when I used it, the fragrance came back.