old age;  old person;  the old;  the aged
 dotage;  feeble-minded old man;  senile old fool;  dotard
 to become decrepit;  to become senile
 to become decrepit and ugly with age
 remaining years (of one's life)
 to grow old;  to weaken with age;  to become senile
 be guided by your children when you are old
 study hard while you are young; (lit.) boys grow old easily but getting learned is harder
 repetitious harping of the elderly;  oft-repeated tales by old folks;  tedious and repetitive talk of old people;  old man's rambling
 trust the judgement of the experienced; (lit.) an old horse won't forget the way
 preparation for retirement;  preparation for old age
 growing old together (as a married couple)
 even an outstanding person becomes inferior when getting old