Ever heard of Chesterton's fence? I don't believe we are more clever than our mother, the computational machinery of the universe. If we remove death, there will be great consequence.

Heck, it's arguable that the slow decline and death spiral we're in on this planet (empathatically NOT just human well-being metrics here), that this is already due to pushing death back, and systematically allowing power/opportunity to accumulate ever more deeply at scale of the selfish individual...

Edit: Maybe there wouldn't be nilihism, but I don't think you could get more fulfilled with the extra time. I feel like an insect that lives 24 hours and a shark that lives several hundred have an equal feeling of accomplishment.