It probably depends on how the genetics play out, how elfish is the person? That would effect the rate at which the animus leaves the body.
Plus, Elves typically do dissipate, but that’s not an apriori requirement. It’s just someone or something needs to grab their animus pretty fast. So with the right preparations, one could move on to an after life. For all I know, and I don’t, there may be elvish religions that have an after life.
Why I say this? Elven liches. You don’t see many of them, relatively speaking. But I’ve heard of at least one. Somehow that elf necromancer managed to contain her animus after death and get it through the liching process.