Sarah could feel his tension, it was hard not to, and she understood it, as she'd long understood his immortality was a curse to him because of the way he loved so many. She couldn't ignore the reality of that curse for herself either, but immortality was a decision she'd made before she had the means to achieve it. What she needed him to understand she had truly made that decision, and that this wasn't only about that. It was still about choosing to be Goblin Queen for and in spite of everything that came with it.
"I'd already made my decision about this, I think," she said, not indicating the box again, knowing he would know what 'this' way, "when I realized I had a way to help them all. But I haven't forgotten what I promised you before." That promise made months ago to never leave him, to find away to make that promise last more than one human lifetime, a promise she'd renewed each time she thought about it.
She cupped his face, needing to look him in the eye, needing him to know how deeply she meant this. "I still mean it, even more now than I did then, if it's possible." It likely was possible, given how each day she learned to love him more than the day before. "So my decision's still the same, even with all the variables." She took a breath, not for this one aspect, but for the weight of what she was about to say, their lives changing with those words. "I'm still going to do this."
She stroked his cheeks with her thumbs, smiling at him, teasing with her next statement, but a seriousness there in the words that was buried very deeply. "But if you get tired of me after one lifetime, the world's a big place."