Of course, that's what "raise" means. Grandmothers also raise their grandchildren -- google "grandmother effect" or "grandmother hypothesis".
I'm more talking about people who want to raise life expectancy from 100 to 200, not go from 70 to 100 (not sure where the original article fell on this).
70 to 100 is clearly possible and we've already gotten a long way there in the 20th century (antibiotics, etc.) The "problem" now seems to be that not everyone actually cares if they live that long... i.e. there are plenty of people who don't want to live to 100, and might not even if they maintained the health of a 60 or 70 year old.
Humans are highly social beings that naturally live in large kin groups. Knowledge and culture form a huge part of our survival strategy. Who among us have the most knowledge and experience to pass on? Elders.
Take a look at the role of elders in traditional hunter/gatherer cultures. Huge importance. Is it not implausible that natural selection would favour increased life expectancy so that elders can maintain and transmit the group's body of knowledge?