My take with much license:
Moreover, the fruit of old age is, as I frequently said, the memory of olden pleasant events, and plenty of them. Also, all things which happen according to nature, ought to be held in a good light. And, what is so according to nature as to die off an old man? Same thing which lays hands on young men with nature opposing and fighting back.
And so young men to me die in such a way it seems, as when the flame is suppressed by a great number of waters (a flood?); on the contrary, old men die thus - when by their own free will, with no summoned force are extinguished as a burned up flame.
And as if apples from the tree: If they are fresh, with difficulty they are plucked, and if they are ripe and mature, they fall. Thus force snatches life from (abl. of source) youth, the ripeness (huh? not accusative?) from old men. Which to me, indeed, is so pleasant that, while (quo?) I come nearer to death, as if I seem to see land and at anytime to be about to come (venturus esse) into the harbor from a long trip.
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What I don't understand:
1. The line; senibus maturitas, why nominative?
2. The 'quo', where's the reference?
3. The line 'quam senibus emori'. Why the ablative?
I was able to get through these with WORDS and a little Spanish: 'que morir de viejo' (lit. than to die from old man), but I'd rather know the actual Latin way these work.