The question is whether or not you'd wish your 77 year old parent/grandparent to undertake 4 years of immense stress.
If your answer is yes I would, I'd like to know why and what factors you consider worth the risk of dying of stress related illness.
To be clear, this is not a job only select 70-year olds can do, this is a job many others want to do and I think if you ask any rational human being, a younger person would be better suited for.