Here is my view purely from a consumer side. When I find a product I like, I get really annoyed if it goes away. This can be true of a menu item at a restaurant or a product at a store. The one store that does this more than I'd like is CostCo. The number of times I've had a product that I regularly buy "disappear" is more than I'd like it to be.
In my opinion, what I would do is have a line of standard soaps that you keep as "regulars" that don't go away, and maybe have some "seasonal" recipes that come and go. Or "special edition". As long as the customer knows that a particular scent or formulation will not be around for a while, then they shouldn't be too upset when it does go away. I don't have any real world experience on this, but this is my plan for my little soaping shop that I plan to setup in the future.