I would be wary of trying to use broad thermodynamic arguments to reason about aging. It is true that our bodies are subject to entropic processes, but we’re also very good at offloading entropy into our environment – that’s pretty much what life is. When a person turns some air and a stack of cheeseburgers into a whole new living person, that involves a substantial local decrease in entropy, even though the entropy of the universe (including all the generated poop and waste heat) increases.
It’s an open question whether an adult body wears out because it can’t be regenerated, or just because it doesn’t. If some organ can renew itself ten times in ship-of-Theseus fashion, there’s no obvious thermodynamic reason why it couldn’t do so twenty times, or a thousand.
It’s like, thermodynamics governs how long a house will stand for. And an abandoned garden will succumb to entropy very quickly. But if a garden is actively maintained, then it can last in the same form indefinitely.
My guess would be that some of a person’s machinery is like the house (teeth, certainly); but most of it is more like the garden, and could go on forever, except the gardener has instructions to salt the earth after a certain amount of time.
