I use essential oils in soaping and found that if I left the soaps out in the open air for months, the scent would slowly fade away. Sometimes the scent would come back a little after a few uses in the shower, but often it would not be as strong as I wanted it to be. I usually scent soaps with essential oils at 3-5% of oil weight, depending on what I'm using (and, of course, would use less if the safe usage rate was less, like with clove or cinnamon EOs).
But then I started storing my soaps differently, and that has helped them retain scent dramatically. What I do now is cure them in open air for 4-5 weeks and then put them into plastic clamshell containers you can often find baked goods in. They look similar to this:
https://www.amazon.com/dp/B01LYH50HW/?tag=skimlinks_replacement-20
I store each batch separately, so the scents from various batches don't combine, and the soaps will stay smelling strongly far, far longer than they used to. In fact, I just went and smelled a salt bar I made 6 1/2 months ago and the smell is still there at about 85-90% strength of what it was the day I unmolded them. I also purchased some cellophane bags to put them in if I am giving them away as gifts, but would like to find a more eco-friendly option. But the cellophane is to help them continue to retain scent until the recipient uses it.