years -
a late time of life; "old age is not for sissies"; "he's showing his years"; "age hasn't slowed him down at all"; "a beard white with eld"; "on the brink of geezerhood"
period of time,
time period,
period an amount of time; "a time period of 30 years"; "hastened the period of time of his recovery"; "Picasso's blue period"
month of sundays a time perceived as long; "I hadn't seen him in a month of Sundays"
aeon,
eon (Gnosticism) a divine power or nature emanating from the Supreme Being and playing various roles in the operation of the universe
blue moon a long time; "something that happens once in blue moon almost never happens"
years -
the time during which someone's life continues; "the monarch's last days"; "in his final years"