People are born and grow up and die of old age in a matter of 5 days. The elders (5 days old) train children and send the most promising one on a trek across the dessert to a monolith that is the cause of the rapid aging to hopefully disable it.
I saw it on a reel to reel in the mid 90's. It looks like it was made in the late 70's or 80's. The cast was small. A few men played the elders seated in a row of chairs and the young boy who had to set out to save them who matures into a man and finally an elderly man.
I've been trying to figure out the title for years.