I think that approaching this whole thing in terms of independence is a great idea. It sounds like you are just coming into creating the "idea" of independence and that might not be the right time. Perhaps feeling that first would be a better time...
I can imagine, if I take a wild guess, that the best time is to say something is when you get to a place where you can talk along the lines of how much you are looking forward to having your own things to do, your own goals and life, all the while loving him and creating goals and a new life with him also. When he says he has some great ideas of what he would like to do with his life and who he wants to hang out with as buddies....At this point he will hopefully realize that you not only need to be independent from him and have your own stuff going on, but that you are excited about it, need it and also love and look forward to be with him... also that he is excited too.
It sounds like he is still very much anxious and nervous and not ready yet. It sounds like you might be jumping the gun a bit and be one step ahead of him; or several. Take a breath and relax into this process. Life is about the journey, not about the end result. You have time and if you take it, you could have something rich, connected yet freeing and nurturing with him.
I don't at all suggest thinking about any other man that you could be with and certainly don't think that planning out details will be at all helpful to your mental health (it could drive you crazy with longing). I think you should put all that on the back burner for at least the duration of a few steps to get to it. This man of yours has huge needs and that should be your focus I think... trust, stability, encouragement, empathy, baby steps to doing things alone.... all need covering first I think before asking for 4 days on and 3 days off or any specifics like that.
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