The topic is short-term ruling vs. long-term ruling.
Leaders like Alexander the Great would be considered short-term rulers because he never really bothered appointing an heir to his throne. As soon as he died, his empire split up and got divided amongst his generals such as Seleucus I, Ptolemy I, etc...his empire basically crumbled faster than it grew once he died. I read somewhere that Alexander said on his deathbed "The throne has go to the strongest." He obviously didn't care much about his bloodline and the future and never planned for it.
This is why Alexander as a King doesn't impress me very much (as a general he was outstanding). He may have conquered the known world by age 23 or whatever it was, but this was because of his father's long term investments in him. Its been said that Alexander was mentored by great minds like Aristotle. His father Philip obviously wanted the prospective heir to his throne to be well-suited for ruling and he provided what was necessary in order to make it happen.
What I'm getting at is if Alexander had invested some time in mentoring and preparing an heir to his throne instead of campaigning for so many years in a row, his empire might not have crumbled so quickly after he died. He might not have conquered the Persian empire and reached the end of the known world so quickly had he invested some time in his sons (either directly through his own influence or appointing mentors to them). However, it could have payed off in the long term by having an heir which would hold his empire together once he became King.
This makes me think he was only after the glory of conquering the world's largest and wealthiest empire of the Persians and didn't care about anything else including the future of the throne nor his bloodline. If you have any sources which prove otherwise, please enlighten me.