One of my posts regarding aging on kurzweilai

De Grey talks about garbage accumulation and recycling it in situ as a solution, but usually unless you have energy to spare the intelligent thing to do with garbage is not to recycle it on site, but to throw it out, and for someone or something to pick it up and take it to an appropriate disposal area.(eventually it exits the body and after that it is somebody else's problem, and someone else eventually recycles it.)

The body has the lymphatic system, and the brain has the glymphatic system

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Throughout most of the body, a complex system of lymphatic vessels is responsible for cleansing the tissues of potentially harmful metabolic waste products, accumulations of soluble proteins and excess interstitial fluid. ...

[In the brain the glymphatic system performs this function... ]
The breakdown of the brain’s innate clearance system may in fact underlie the pathogenesis of neurodegenerative disorders such as Alzheimer’s, Parkinson’s, and Huntington’s disease, in addition to ALS and chronic traumatic encephalopathy. -link

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Even our brains need to take out the trash.

Researchers from the University of Rochester Medical Center found that a waste-flushing system in the brain, called the glymphatic system, is most active when we sleep -- nearly 10 times more so than during periods of wakefulness, in fact.

Plus, during sleep, brain cells shrink in size by 60 percent to better allow for the removal of waste from the brain.-link
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Despite aging glia and aging vasculature(in part due to the telomere shortening), the oldest human lived for over 122 years, they didn't have dementia when they died, iirc, and died from choking according to some sources.   Those exact same billions of single cell neurons were alive at high metabolism for those entire 122 years without failing, providing mental sanity even till the end of life, even with aging surrounding tissue adversely affecting them(tissue responsible for garbage removal, nutrients, etc). 

[quote]

Using this method, Dr Frisén has shown that most cells in the body are less than 10 years old. -link

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  If garbage accumulation was a problem for a cell with an insignificant fraction of that[neural] lifespan, as most of the rest of the cells in the body are, pray tell how did these billions of cells managed to continue working at all decade after decade after decade?

Also to still be able to sustain high metabolic activity even at 122 years of age, the mitochondria must be working to at least some decent degree, probably a bit adversely affected by surrounding aging tissue, but there seem to be mechanisms to preserve mitochondria quality like mitoptosis, there appears to be genetic regulation that keeps mitochondria quality in check, and it is dysfunction of this regulation that may be behind a loss of mitochondria quality.

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Thus, suggesting that mitochondrial dysfunction is a good enough reason for eliminating mitochondria and as Dr. Skulachev says, mitochondria follow the samurai’s law; “it’s better to die than to be wrong”.-link

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As for cancer we have the case of cancer free centenarians who smoked two packs a day for decades, and died cancer free.   Would be very unlikely cancer didn't actually pop up.   The likeliest scenario is it popped up and the immune system handled it, at least this seems the case for some fraction of the population.-link to original thread