It's not just great grandparents, but the family calculus on grandparents changes significantly as well. If my parents were 35 when I was born, and I don't have children until 35, my parents are 70. With a life expectancy of 80, my children never really get a chance to know my parents. Whereas if each generation is having children at age 25, my children will likely be able to know their grandparents for 30 years.

I have no idea if it's good or bad, but it's interesting to think about. I do have to wonder if it affects how younger people perceive the past, since they have less of a direct connection to the past.