These advanced being-aliens are not from the future. Time travel for them and all beings, for that matter, is impossible regardless of the technology that they possess. Even God cannot time travel!
We don’t die! When it is our time to leave the planet, we never lose consciousness; we are, at the time of death, not only conscious but feeling really good because at the time of death we are administered a drug which makes our transition much easier for all involved. In just a matter of seconds or in the blinking of an eye, we are transported from here to our next home out there. Death is the greatest kept secret and it is a secret for a reason.