for a long time; for ages
Adverbial form of 久しい, used to describe a state or action continuing over a long period. Often used in written or slightly formal contexts.
See also: 久しい
I haven't seen him for a long time.
This town hasn't changed for ages either.
Adverbial form of the adjective 久しい (hisashii), which has been used since Old Japanese to express a long passage of time.