Let me say first that if this request is for a lost loved one, my sincere condolences.
My rather pedestrian suggestion:
Numquam moriuntur, qui in corde manent. (think present indicative
moriuntur is best here, as it makes it a statement of fact rather than a wish or prediction).
But I'm interested in what others would do with this phrase. I suspect there is a similar sentiment expressed in a classical or religious text (I can't think of one, but it's late) that you may prefer. If anyone can come up with it, please post.
Finally, please review the
disclaimer at the head of this forum.