Elves: truly immortal?

[tom bombariffic]

Ok I got bored reading some of the really long posts cos im tired, so someone may have said this already, but I noticed a lot of people are saying that once elves are slain or pass away with grief, their spirits remain, and then some come back in different bodies, or in very similar forms. So why does Glorfindel come back as Glorfindel? I was led to believe that he dies, and comes back later in the exact same form. Although Im probably wrong.

Oh and whoever wrote the last post has obviously been reading even less of the posts than me - elves "dying" in battle has been covered umpteen times in this thread alone.