Good to hear, Z.
In some ways, your post was mildly amusing. After all, as a member of a long-term same sex couple, you probably have a lot of thought that's gone into the nature and value of relationships that many hetero folks might take for granted. In that regard, being mindful of your (now plural) relationships might even be easier for you than others. It is great to see the excitement and to have a positive environment though. I'm glad you're off to a good start.
That said, let me remind you that while love may be boundless, time is not. Your original partner is wise in noting that time with each other is important. As you head down this road, remember that communication is a vital element, and the other is time management. If you need any unpaid and perhaps brilliant or perhaps highly suspect advice, you know where to find us.