Help!!! Do native speakers say something like this ?

Hello, everybody! My student asked me a question: Do native speakers say it in this way?
1) I haven't seen you for a long time.
2) I havn't seen you for long.
3) I haven't seen you for ages.

Can the verb SEE mean an action lasting for a period? (I don't quite think so.) If it doesn't mean an action lasting for a period, how can we use "for a long time" or "for ages"? Many Chinese students say it as 1). Is it right? Why?According to Oxford Dictionary, "for a long time " is usually used in positive sentences,while "for long" is used in questions or negatives. It means the sentences above are ungrammatical. How can we distinguish "for a long time" and "for long"?Can you explain these phenomena? Thanks a lot!

Hmm... this got me thinking:  What is more appropriate: "for" or "in?"  Is there a general rule?

So is "I haven't seen you in ages." acceptable as well?  "I haven't seen you in a long time." sounds alright to me.

"I haven't seem him for a while." sounds okay but now I'm not so sure about "I haven't seen him in a while."

Oh, and there's that other expression: "I haven't seen you for eons."  Makes me wonder as well, where could've this originated from?

Cheers!