I think they go stale after a while. How in the world can they grow new healthy sperm when they can’t grow hair?
They can’t go stale, they are cycled out of your system with or without any action on your part. Hair? Are you kidding? I was balding in my 20s and had three healthy kids and I know others who were completely bald in their 20s who had 4 or more healthy kids. Maybe if you are bald below the waist, but then that indicates a hormonal problem, not an age problem.