I know that actually, human lifespan is always reducing from each period. But I dont expect it to be only for 40 years. If the average human lifespan was 40 years, I think how the world runs will also be different. If you only life until 40 years, I think you will not see your grandchild if you married in 25 years-old. Also retirement will not related anymore. As people on my country usually work until 60 years, then retired.
I think all the work for the middle class will be switched to remote work. So we can take vacation during works, then no need to think about retirement, because we already on holiday everyday. People will married younger, maybe on 16-18 years old so they still can meet their grandchild. Insurance will be more expensive as the risk will be higher. People will take a college after getting some work. The minimum age for work no longer at 18, maybe it can be 14 years old. More business will switch to family business approach because the founder will have least time to build their business. They will inherit their business to their child to make it more successable.
I think we will work harder to meet our long-term goals, because of the life expectacy reduce. But nobody knows how it will works if the average human lifespan is only 40 years. But I will do freelancing and remote work as soon as I clear my study, while I take a higher education. Living by the needs to bear other people will not related anymore.