Doesn't literally EVERY elf live until the end of the world? Like their body may be slain but their spirit just returns to Aman to chill in the Halls of Mandos with all the other 'dead' elves until Iluvatar summons them to fight in the final battle. Even then you get Glorfindel just too Chadly to stay down, he walks right out of the halls with a blessing and sails back to middle earth to terrify nazgul. Not every elf was born in Cuivenen and exists for the entire duration of Ardas history, but every elf sticks around in some form or another until all creation is destroyed and remade. That's why elves choosing to be mortal is such a big deal, they actually die. Their soul isn't returned to their family members in Aman to catch up, they go wherever men go. Didnt Feanors mother's (Idril?) soul get so damaged by (implied) rape that she was set apart in the halls? She died and still went to the halls but was basically catatonic forever. She still 'lived' in Aman until the Dagor Dagorlach, even though her injuries were so terrible she probably longed for death. That sounds more like eternal torture than eternal life, but either way its forever, she didn't get oblivion or whatever happens to men.