One of the problems with immortality is that it removes all ethical and moral barriers. The longer the time, and the fewer the penalties (death, incarceration, moral turpitude), the possibilities for excitement and new experiences dwindle, and cognizant humans will find some sort of diversion, anything which will stimulate and excite them, which will broach current law and accepted ethics.
Almost all law and acceptable behavior is based around a lifespan of 100+ or - 10 years.
I actually wrote a philosophical essay on this at some point because I found the idea more complicated than I had previously thought.
Imagine what happens to a person who has read every book, listened to every opera, seen every movie, and is inundated with the same, repetitive, cyclical, cultural waste which is laid upon him every decade or so. Nothing will stimulate the same way the first sunset, the first caught fish, the first kiss, the first lay, the first great sleep, the first breakup, will do.
The only thing which will remain is murder, or torture, or relegating other humans to the walking flesh sacks that they are. The interesting aspect would come in with an immortal, already cannibalistic, sociopathic serial killer during his mortality.
What would then give him stimuli to have the will to continue existence?