Hi.
I have thought about this a lot in my life. It was my go to suicidal fantasy. Made my own plan to disappear forever too in hopes that would alleviate the pain even if just a tiny bit. Better to go missing than them knowing I had died, maybe. In the end I'm not convinced of that anymore, never really was, but desperation and love for those around you make you cling to any fantasy if it makes it easier for them, and for you to justify the pain you'd bring them. It's sad all around but it shows you do care a lot for them even in your own suffering and in the point of having to consider this, I'm sorry for that but I feel you.
As for your question and my experience on it, I don't think it is a good alternative or plan. I learned that the lack of closure when someone you care for disappears can be just as bad, it is awful. The constant worry, stress, uncertainty and dread on what might have happened to them, if they are arright, or dead, or anything, the mind just races constantly and you can age pretty fast. If that comes in succesion to finally learning of their death, sure that's closure, and puts an end to that consuming worry, but it's not worth it to make them go through that first at all if you care for them.
Again I know why you might think it could be best, when the urge is so bad you cling to any posible loophole but really there are none, and this one I think adds to the pain.
I too have this impression that it may hurt less rather than say, finding you dead in your apartment.
But we don't have much control over the pain of those who remain, in the end it's gonna hurt them anyway, whatever you do.
If anything I've learned that closure helps. A letter, stating what happened, sparing them that worry. But that latter sentence is true too, that's the only bit you could spare them the rest is inmense pain.
I really hope you two don't get to that point and can actually overcome this shitty urges of the brain, or your situation improves and you can spend more time and cherish those you care for, because you clearly do. Lots of hugs <3