They are yours!
Vampire leaders tended to enter into eternal slumber before reaching their peak age. There were many possible reasons as to why they chose to do it. Be it because they believed that they had accomplished everything they could hope for, or because they felt that it was time for a new generation to decide the vampires' future.
Vincent Eno's theory on the matter, however, was an entirely different one. He had stipulated that the reason they would make that choice was a lot less selfless, and rather quite selfish. It was something vampires would do… out of fear.
As a long-living species, they were blessed with a few centuries in which they would continuously grow stronger, yet it was inevitable that at some point the ravages of time would turn against them. Instead of growing weaker with each passing day, they would much rather be remembered as the bastions of strength each one of them represented.