What is the lifespan of the average alien Grey?

The alien Grey lifespan is approximately 300 to 400 years, and that limitation is due to the fact they are artificial and they are subject to degradation from entropy, and this is true of all physical organisms. To undo these factors and do a meaningful repair requires a quite high-level rejuvenation mechanism. They have not fully achieved the mastery of the eloquence of human physiology, nor that of Arcturians, and this is partly intentional as well on the part of the Arcturians, to have some control with regard to the eventual demise of the Greys as a kind of checkpoint to not let them outgrow their place, so to speak. They are indulging the personal quest of the Greys to understand human emotions and strive to create a soul to enable their reincarnation, as they know the other beings around them are immortal and desire this for themselves. As we have told you, they will not and cannot succeed with this, as the creation of souls is beyond any organism regardless of their pedigree. So it is folly but nonetheless has been a driving force for manipulation of human as their guinea pigs.