User blog comment:Frieza Sama/Favorite Animes/@comment-3256091-20101226044353/@comment-3256091-20101226113322

Well Misa's life span as seen by Rem was 5- (followed by 4 digits) while Light's was 3--- (followed by 7 digits) So if Gelus had a 100 years of life in him left, Misa was given that 100. Then she made her eye deal twice, cutting her life to 25 years. But Light's was much more. I think Ryuk saved Light from shame of having to face Near and the world realize that he was Kira.