Most natural scents fade, and that's probably why fragrance oils are so popular.
Ive had better luck grinding spices into oils as well as infusing, such as star anise. I put about 2 handfuls into 1-1.5lbs of oil, let them infuse on a low heat overnight, blended them, left them for a few hours, blended, left, blended, left, blended, left, then added lye and made soap. Gave a beautifully rich red-brown colour, and made any soaps close to it smell like star anise for 3-4 months. It faded eventually, but is the most successful strong scent Ive had. For a subtler pleasant smell I infused and ground a load of lemon rind and some chamomile in the same way, you really need to keep blending and resting though or the rind drys hard and gets quite scratchy.
Anchoring essential oils with clays, cinnamon oil, and corn starch helps... but will fade eventually, and can work out expensive. I made a lovely shave soap this way, with about 200 drops of basil, lemon, and tea tree. 6 months in and it still smells good.
Ive also been experimenting with putting EOs on surface of soaps after 12-24 hrs and letting them absorb in like excess oils do. Some take better than others, but I'm liking the results. Also making soap dough and adding scent after a few days is kind of the same thing. Just make sure to research your EOs before you use them.
Also, rebatches and adding eos after hp cook holds scent better
