Sleepless = food?

Right, before the simple "No" comes out, here's the situation. I'm F2P and naturally getting light and dark is proving to be a pain. However I do have a 6* DA, and with altar purchase I can slowly get her to 9* (can make 6* Dark spirits easily enough). I also have ONE Sleepless. Is it worth holding onto him for any reason instead of just feeding him to my DA and getting her up to 9*?

Thanks in advance