A lot of people tend to forget that AD&D Elves are not exactly the same as Tolkien’s elves.
Long Lived Elves vs Immortal Elves
AD&D 1st edition elves grow old and die. Although long lived, they go through lifecycles. Tolkien’s elves reach adult maturity and then apparently stop aging.
Youthful Stature vs Greater Build
AD&D 1st edition elves stand around 5′ tall and have a slight build. Tolkien’s elves are typically man sized; some older elves stand much taller than most men.
Tolkien’s elves are tied directly to the cosmology of Arda (the world of Middle Earth), and by design are meant to grow old within the world, until the final breaking of the world.