"There is just nothing to select for longer lifespans beyond the time it takes to reproduce."

Definitely there is. If humans spent a long time learning, and were more productive and fruitful in their later years, developing more intelligent systems, they would theoretically out-compete a civilization that wasn't able to develop such advanced skills and learning - especially related to passing on information.

The missing issue not obvious in genes is the amount of cultural information and learning passed on. A genetically 'superior' race of beings (faster, smarter, more disease resistant) would surely be 'beaten' by a group of lesser beings who were able to cooperate, learn, cognize, master tools, pass on wisdom etc...