Well, your idea does not always work.
First, we have dictators that seem to defy death. Case in point is Mubarak. I was in university when he came to power, and 30 years later, he was still in power, when the revolution erupted, with all the tumultuous aftermath. Oh, and he is still alive at 88 years old! You can also count Ali Abdalla Saleh of Yemen in the same league. Although he was deposed, he is still alive, and meddling with his country's affairs (aided/co-planned the Houthi take over which is still going on, and causing the Saudi shelling).
And then you have those who just hand over the country to a new generation. Hafez Assad died in power, after several brutal decades. His son, Bashar is now the one causing all this misery on his people.