Yes, of course. Given that they are going to die regardless, using the elderly for experimentation seems reasonable. We could be as humane and considerate and provide anaesthesia and care as much as possible, but it's a false kindness to let the dying die because trying to save them is risky and uncomfortable.

With twenty years of massive effort like this, and hard risk taking, would we have improvements against aging? Would the human-years saved be massively greater than the human-years we lost in experimentation? I think both answers are likely "Yes".