In the first sentence you are talking about Natural Selection, not "evolution". The two are not synonymous.
An organism that exceeds its reproductive period is not necessarily useless. Remember that evolution happens to species, not individuals, and an evolving species by definition has to have generations.
An organism that lives more than twice its reproductive lifespan again can have plenty to offer its species, whether it be in defence, hunting or -- in a species like ours where information is the main fitness currency -- education. This could have a massive effect on the overall rate of reproduction, and it would doubtless be a major selective advantage for the generational groups with the greatest number of most "experienced" elders.