A very interesting subject. We've been fighting against death since we were a single cell organism. Infinite life is not worth even considering, but extension of life is. It's hard for a 25 year old to know what a 60 year old understands. Therefore, the longer the lifespan, the more capacity to collect knowledge and mastery of the our world and the wisdom to use it.
If I understand correctly there's a strong correlation between a low average age and the likelihood of a failed state. At the other end of the spectrum, older populations are much more stable, cooperative, and less violent. An older planet may be a calmer, wiser planet...of course there's also the fact that few will be working to support the many...many sociological changes will need to happen to ameliorate that. Reduction of what we currently call quality of life? Extension of working years?