They sure can double-up for daily use. I use Neutrogena Triple Moisture Silk Touch Leave-In Cream. It's the only thing that I found that moisturizes as well as softens my hair. Products marketed as moisturizers never seem to work in my hair, I guess I need something stronger. I was told that leave-ins penetrate the hair strand, whereas moisturizers only coat it.
The good thing is, is that I can use a lot (so much that it makes my hair damp) but it still won't revert my hair. By the morning my hair absorbs it all and is still soft, straight, and shiny. I love it, and it's one of the only non-Ayurvedic items in my regimen