advanced age
advanced years
age of retirement
an incurable disease
anility
changeableness
childishness
corruptibility
death
debility
decline
decline of life
declining years
decrepitude
dotage
dotardism
eld
elderliness
ephemerality
ephemeralness
evanescence
feebleness
finitude
fleetingness
fugacity
green old age
hale old age
hoary age
impermanence
impermanency
incapacity
infirm old age
infirmity
infirmity of age
insipidity
instability
invalidism
longevity
momentariness
mortality
mutability
old age
oldness
pensionable age
perishability
ricketiness
ripe old age
second childhood
senectitude
senile debility