Good plan 👌>return to human body
>get cancer
>die at age 55
E: "Modern" humans aren't actually humans at all. They're aliens who look like humans."But wait! If they lost their ability to reproduce, why there are still flesh humans around?"
A: they lied. They never lost the ability to reproduce, and instead they had class segregation between the ones that could afford a gray body and the ones that didn't.
B: they told you only the convenient part of the story. Through decades of genetical engineering and body modifications only the leading class and the elite lost the ability to reproduce: in order to not die out they resorted to the gray bodies.
C: the cause and the effect were reversed. They lost the ability to reproduce BECAUSE they resorted to the gray bodies: the ones that stayed human kept living normally.
D: ThErE mUsT bE a WaY tO aRtIfIcIaLlY bUiLd HuMaN bOdIeS aNd ThEn TrAnSfEr A cOnScIeNcE tO iT!