I've always admired Jim Shooter's LSH story "Soljer's Private War" (Superboy and the Legion of Super Heroes 210: August 1975). As readers of my Infinite Earths story "Sweet Adeline" will remember, in my LSH 3023 story arc, Adeline Kane's epigenetic latent immortality was activated by a blood transfusion from Slade Wilson, her immortal husband. Throughout the centuries, she encountered many other mortals and immortals. One particular one was Private Michael Essad, a soldier for the Icelandic Alliance during World War VI in the twenty eighth century. And herein lies a cruel aspect of the laws of time insofar as they affect immortals who fall for mortal humans, for although Adeline knew Mike Essad was fated to die twice, historical rigidity and the consequences of temporal anomalies incurred if she acted otherwise meant she could not save the man she loved- not once, but twice. 

Incidentally, readers of my "Sweet Adeline' story will also recall that when she met R'as al-Ghul at her daughter Rose's graveside, he told her that he knew what she was going through, because Talia wasn't immortal and several decades beforehand, she had passed away. So, there's a story challenge for anyone who wants to undertake the depiction of that event. How did Talia die? Did R'as know beforehand? What role did Batman play in the proceedings, if any?  And what did it do to Bruce, given the bond between Talia and him?