I think it sounds great! And the fact that you are all happy within this structure would seem to indicate that it works very well for the three of you.
I am someone who, for now, would like to be independent while managing multiple relationships (when poly really gets rolling in my life). I'm not really interested in cohabiting with a mate again, nor of being in a blended household or tribe. That may change when the sting of my divorce isn't so strong, but for now, if I were in a situation such as yours, I think splitting time in that manner would work very well for me. It would seem like a great way for the fulcrum in the Vee to give fully to each relationship without being distracted by scheduling conflicts and anxieties over making sure everyone's getting enough attention that I see so many people here dealing with. And those in the position of the arms of the Vee know exactly what to expect. I also think it's great that there is flexibility built into your arrangement, that texting and calling either one is something unrestricted for her, no matter whom she is with. This sounds sane, healthy, and based on trust.
There's a lot of good to be said for STRUCTURE, and freedom is definitely something that can be nurtured within a clearly defined structure, though we often think it would be the opposite.
Heck, I think it would even work for me if I were not married. There is a guy I went out on a date with whom I would really only be able to see on the two same days each week (because of his work schedule). If we continue and develop this relationship (I'm not yet sure if I'm interested), he would be my "Monday-Tuesday boyfriend," which I would think would make it easier to make plans with others in my life. Knowing the parameters within which a relationship with him would have to operate, gave me a sense of relief, in a way.
I know you have shared this with us before, but thanks for reminding us of how you've worked it out and giving everyone something else to ponder, as far as dynamics/configuration.