[google234123]

The fact that these naked mole rats live 30x longer than other rodants suggest life spam can obviously be controlled. Anyway, I can imagine increased life spam as just costing something (not free) - e.g. you spend more energy on error correction and detection.

[jjallen]

the fact that each species tends to live its own lifespan and each lifespan is somewhat unique (like not all species tend to live 10 years, for example) suggests that lifespan is genetically programmed.

There are some good, obvious reasons to not have parents and grandparents around forever in limited resource environments.