Hi! I have a couple friends who thought that CP soap, in general, would last longer than M&P soap with regular shower use. There is a specific scent they both love and were using in their M&P bars, but they were going to ask me to make CP soap with it so the bars would last longer. I gave them some of my CP bars to try (with other scents) that had cured for about 5-6 weeks, and they said the bars didn't seem to last any longer than their m&p. Those bars I gave them to try were made with OO-60%, CO-20%, Lard-15%, Castor-5%.
I realize there are lots of variables, but since that time, I've upped my percentage of lard and lowered my OO, and also started using sodium lactate just so I can demold my loaves more quickly and without having to freeze them. Does sodium lactate also help with longevity? I also told them that the longer they let a CP bar sit and cure, the harder it will get and the longer it should last. I don't think they want to do an all-OO bar and wait a year for the curing.
So I'm just looking for suggestions about things I can do, add, remove, etc., in order to make a bar that lasts longer in the shower. My current recipe is OO-35%, Lard-35%, Rice Bran Oil 10%, CO-10%, Castor-5%, Shea-5%. I love how these bars are behaving when I use them, but still trying to instill more longevity

Thanks in advance!