Emerikol
Legend
It all depends on how you look at aging. Let's suppose we posit that aging for purposes of this discussion is the eventual decline brought about by time. Let's also suppose there are creatures that age at different rates including potentially a rate of 0. This is what time does aging wise.It shouldn't. Long-lived species are simply more resistant to magical aging. Elves are serially longeval (Tolkien-style) in my settings anyway.
So an elf would grow to maturity and then would never change appearance indefinitely if they are immortal.
A dwarf who let's just say ages 5 times slower than humans would change as time passes but at a slower rate.
So what is a ghost's aging doing to you? That is the question. Is it duplicating the effect of time and thus would affect elves, dwarves, and humans linearly? That is one option. Another option is that it is not duplicating time at all but ravaging the body in such a way that our lifespans appear changed. If so, then a human might age 40 years upon seeing a ghost, an elf who is immortal might no longer appear 30ish in human years and instead appear 70ish. That elf might still be immortal. The aging didn't kill the elf but the elf was affected. The dwarf could age 200 years because that is 5 times the 40 years because the effect is to ravage the body.
Either one of those approaches could be true in any given campaign. They are plausible if aging due to fright is plausible or a given in a fantasy game.