Nouryia, you might be over-analyzing NRE. Yes, it can last for extended periods or short periods. You seems to be on the long plan.
Part of this might be because of the accidental fall-into-poly situation. Think of it this way, when you started dating as a mono, everything was shiny and new. It took time to adjust to what it was like to meet someone new, get to know them, adjust, and progress or move on. You've basically started that whole thing over again.
Yes, you have relationship expereince, but this is relationship plus relationship. Not only is it novel and new in particular (new person), it's new in general (new lifestyle). That's bonus NRE. I also call this PAS (Poly Adjustment Syndrome).
As poly becomes your new normal, this will quiet down. In the meantime, your capacity for love will grow. You might take a moment or two every once in a while to do things for your husband that remind him how great and loved he is. I find that with my wife, doing something with or for her specifically when she knows I would normally be somewhere else reminds her that she important ("Why, yes, honey, I was planning on being there, but I just really wanted to see you and give you this. That can wait."). I'd suggest the same for your new man and his wife. Any time a new partner comes in, it's a tranisition for everyone. You might even consider sitting down with your new man and brainstorming. You might find that coming up with ways he can make his wife feel special and while he thinks of things that would make your husband feel special could introduce some novelty into the original unions while also helping everyone feel more connected.
Worry less, have fun, and be well.