is an adverb meaning "long ago", "ages ago": something finished well before now, or well before the time you'd expect. It goes before a verb in the past tense, or in the ている-form for a state that has held for a long time.
。
I finished my homework ages ago.
。
The film started a long time ago.
。
That shop has been closed for ages.
The event is over, so the verb is never in the non-past.
With or , it often carries an edge: you should have known I knew.
、。
I've known that for ages.
とっくに or もう
means "already" and says nothing about how long ago. とっくに adds that it was a long time ago, often with surprise that someone hasn't noticed.
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とっくに is conversational but fits polite speech as it stands. In writing, or takes its place, and is the emphatic spoken form.
。
The deadline has already passed.
、。
I forgot that story ages and ages ago.
Lingaku