Biological immortality, or negligible senescence, is not invincibility. Accidents, violence, and catastrophic disease would still matter. Instead, it means the cessation of aging for a core population, and with the more realistic aim of bringing aging itself under medical control. The body could be maintained, repaired, and restored well enough that a person no longer declines simply because time has passed.

The key components would include advanced gene editing, disease prevention, cellular repair, organ regeneration, immune system renewal, and direct intervention in the aging process. Genetic disorders would become preventable or repairable. The goal is to prevent or cure nearly all diseases, but for sure, most major diseases would be detected early, corrected, or avoided before they caused lasting damage. 

I think humanity could reach this threshold around 2200 because several fields are now converging: AI, biotechnology, gene editing, cellular reprogramming, regenerative medicine, and eventually nanotech-scale repair. None of these alone is enough. But together, over half-dozen generations, they will give us a working command of human biology. As that happens, aging will shift from an unavoidable fate into a managed condition. Not eternal life. Not magic. But negligible senescence: a body that can keep renewing itself as long as repair keeps pace with damage.