The longer you let it cure, the more mild the soap will become. And yes, there is a big difference between a soap that has cured for 2 weeks and a soap that has cured for 4 weeks. At least to my skin there is.
Also, I find that my soap lathers better, creamier and more long lasting lather, the longer it is cured.
I recently found a bar of soap from a batch that I had made about 5 years, ago, before I really got into it. Wow, that soap is so fabulous! I am hiding it so no one else in this house can use it. I am hoping to stumble across another couple of bars sometime around here.But seriously it is such nice soap now.