Thread:Thorin Stonehelm/@comment-26361236-20150605003909/@comment-27718380-20150607163445

Yeah they do age physically but very, very slowly. The cycles thing is a reference to the books somewhere. They do not age physically, no, but they become more weary of the world and feel its sorrows more. As they can die of their grief and weariness, eventually they will die from the sorrows of the world overcoming them. Therefore (except in blissful lands like Valinor) eventually they will die from their grief. They may seem immortal, but they age through mental stress which eventually overcomes them.

take a look at this: http://tolkiengateway.net/wiki/Elven_Life_cycle#.22Cycles_of_life.22_and_aging