Spaceship,
I don't know what happens if you take two, probably nothing, as the first (in my mind anyway) works by ensuring steady state no decay DNA replication.
Chris, I hate to say it but the "reduction" you speak of could easily be to do with nearly six decades. If you were held at thirty the "reduction" problem might not occur at all.
Certainly my capacity may well be reduced; I've not exactly taken the best possible care of my synapses
Still, the fact holds that our memory capacity is finite, and our capacity of organising that memory considerably more so; how ever well brain cells are regenerating (who was the author of the short story where immortality was achieved by perfect cellular regeneration, which perfectly returned brain cells to the state in which they had been before the treatment, ie without any extra memories? Sixties,I think) there is a finite quantity of potential storage, and you are trying to put an infinite quantity of disorganised information into it
and put the nescessary links in to be able to refind it. Mathematically improbable.
So, while unfair wear and tear might have an influence, in the long run nobody's brain's properly designed for the really long run.
Racist joke
Man goes into a transplant clinic for a brain transplant, and is showed available models
"and here we have a colledge professor, only one careful user, well run in, $150.000"
"Interesting; and this one?"
"Hardly used, the star of a soap opera, masses of free capacity $100,000- and here, our star offer, from a swiss german, $450,000 !"
"But why's that one so expensive?"
"Oh, sometimes you have to open fifteen, maybe twenty swiss germans to find one"
Easily modified for whichever nationality/sport you wish to criticise at the moment…