I was recently introduced to evolutionary theories of aging in the book Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness. See the "Aging" section of this lesswrong book review for an overview, or these wiki sections on antagonistic pleiotropy. The core concept is that there is selective pressure in favor of mutations which benefit an organism early in life but harms it late in life. This is because organisms die of other causes, so will have a lower chance of reaching the age where the mutation becomes harmful. A higher the rate of death from these other causes, the lower the natural lifespan of the organism.

If that is an accurate description, there would be many different issues that only emerge later in life. The lower rate of production might be a adaptive feature, which partially avoids the negative effects of these harmful-late-in-life mutations. Removing the root cause of lower production could then be harmful. I would expect there to be many distinct issues, and many distinct "root causes" that were evolved to optimize around those, and that the age of onset would generally be in line with its natural lifespan.