RP, I wouldn't worry about poachers in your relationship, you guys seem pretty solid.
You mentioned poachers in your first post here, and that seems like a good term. And if any animal poachers get offended, well good for them.
In general, I don't feel that any third party can come along and break up a happy, healthy, functioning relationship. Like concrete, there has to be some crack for the water to seep in before it starts breaking it up from the inside. A good solid foundation with proper ongoing maintenance will prevent such seepage.
To the poster who was in a network of 12+, it seems like that's a lot of people to have an extended tight communication network. Lots of room for cracks. I can't even maintain 12 casual friendships, so 12 romantic connections would be well outside my realm of possibility. Someone who's loosely on the fringes of that network would be "easy pickings" for someone who wanted them all to herself.
Gralson: my husband (works out of town).
Auto: my girlfriend (lives with her husband Zoffee).
The most dangerous phrase in the English language is "we've always done it this way."