One thing to add to this based off of the comments of "where do we go from here, we're like halfway through" I think it's at least possible each of these ladies has the option to bring in a 3rd for a scene or two (late night wine drinking, anyone?), or a scenario where we take a mutual break from our relationship, or certainly the option to call it quits and say it's not working out.
But, that all speculation aside, considering the quality of this game I frankly wouldn't really care if I had to have 5 or 6 playthroughs to get everything and instead in each save focused on my individual story with the lady above (in order that order... still debating swapping 1 & 2) while devoting the remainder of my time 100% to running the most efficient whiteboard B&R has ever seen and also getting my DIK bros all the ladies they can handle as the ultimate wingman. Derek will never have had it so good.