An interesting hypothesis - given that perhaps the oldest of all Eldar are those Harlequin who guard the Black Library - some of them supposedly being alive when the Old Ones were still around. As some of the only permanent residents of the webway, that would explain a lifespan of potentially millions of years within the immaterium.
eldar aging is only a "recent" issue, because before certain chaos gods f***d up the warp their souls was capable of reincarnate. (is proballly not and eldar exclusive, but of all the psy capable race).
