Learning to not care about death and losing it all at a vary young age would make their life even more relaxing than a life which clings onto luxury and expects to never lose it until death. Not sure about the roman emperor anyone here is talking about but this isn't a lesson you can learn easily later in life. You will never be stable for life again. A good example of instability is what's written about the dictator caesar tugging through a desert, not asking for water and when a light solider came up with water in his hood, he said the equivalent of thank you, took it, then poured it down into the sand. This is somewhat saner than what spartans would do.
Not sure if it's true because of how history works.