In more ways than one, just about everybody here is trying to tell you, storing already diluted developer is not recommended. That is not a good idea. It is risky. Kodak tells you not to do it. No one here does it that way. Further, none of us have any data on diluted developer that is half full. You are, of course, welcome to do it anyway you wish. The result may be good, bad, or different each time.
If you are looking for "n day" type answer, and that is the only answer you'd accept, I don't think you are going to get it.