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Get ready for some confusion! LOL. Could you check these and tell me what you think?

1) I haven't used it in a long time.
= It's been a long time since I last used it.

2) I haven't used it for a long time.
= Same as #1: It's been a long time since I last used it.

3) I haven't used it (for) long.
= I have always used if for a short time. I've never used it much.
= Same as #4: I have been using it for a short time.
("for" is rarely included)

4) I haven't been using it (for) long.
= I have been using it for a short time.

("for" is rarely included)

5) I haven't been using it in/for a long time.
= This is odd and is not used.

If what I "supposed" is correct, then... I wonder if structure #2 could also mean the same as #3 or #4. If that was the case, it can be very ambiguous if taken out of context.
Any comment will be appreciated. Thank you in advance.
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1) I haven't used it in a long time.
= It's been a long time since I last used it. OK.

2) I haven't used it for a long time.
= Same as #1: It's been a long time since I last used it. OK. But I like 1) better for this meaning.

3) I haven't used it (for) long.
= I have always used if for a short time. I've never used it much. I wouldn't put it this way. always and never are puzzling. I'd paraphrase: I have only used it for a short time. (that is, not more than a short time)

= Same as #4: I have been using it for (only) a short time.
("for" is rarely included) I agree.

4) I haven't been using it (for) long.
= I have been using it for (only) a short time.

("for" is rarely included) I agree.

5) I haven't been using it in/for a long time.
= This is odd and is not used. I agree in the case of in a long time. On the other hand, for a long time isn't quite so odd to my ear.
KooyeenI wonder if structure #2 could also mean the same as #3 or #4.
Yes, that is very remotely possible. I think the native speaker's first reaction is not to see this possibility. The first reaction is to hear #2 with a meaning different from the meaning of #3 or #4. I think the native speaker can only see the possibility that all three might have the same meaning when his attention is drawn quite strongly to that possibility. And even then, it's what I would call "a forced reading".

CJ
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Ok, thanks! [Y]

It's not clear to me yet what #3 means though, and I am not sure about several other things... I'll try to keep this short, let's see...
I'll make up some dialogues, just to check what I should say in similar situations.

Scenario 1 (No one is playing)

a) They say that if you play games on cellphones like yours for more than one hour it suddenly heats up and it stops working. Is it true? Does yours have that problem?
b) I don't know, I haven't played long (yet)... / I don't know, I've never played long on my phone... / etc.

Is that what I'm supposed to say? Any other options? How about using "for a long time" with "never"? Ex: I've never played for a long time on my phone, so I don't know if it heats up.

Scenario 2 (One of them is playing)

a) They say that if you play games on this cellphone for more than one hour it suddenly heats up and it stops working. Is it true? How long have you been playing?
b) While playing, or after pausing the game - I don't know, but I haven't been playing long... maybe half an hour.

Is that what I'm supposed to say? Other options? According to my previous post, "I haven't played long... maybe half an hour" should be ok too, but for some reason I believe most native speakers just choose the continuous tense for this meaning.

Thank you so much again.
Scenario 1 (No one is playing)

a) They say that if you play games on cellphones like yours for more than one hour it suddenly heats up and it stops working. Is it true? Does yours have that problem?
b) I don't know, I haven't played long (yet)... / I don't know, I've never played long on my phone... / etc.

I don't know; I've never played that long on my phone. (Meaning: There are no occasions on which I have played for such a long time on my phone.)

Is that what I'm supposed to say? Any other options? How about using "for a long time" with "never"? Ex: I've never played for a long time on my phone, so I don't know if it heats up.

more than one hour was specifically mentioned, so I'd stick with that long in place of for a long time. Still, you can say I've never played for such a long time on my phone, so ...

Scenario 2 (One of them is playing)

a) They say that if you play games on this cellphone for more than one hour it suddenly heats up and it stops working. Is it true? How long have you been playing?
b) While playing, or after pausing the game - I don't know, but I haven't been playing long... maybe half an hour.

I don't know, but I haven't been playing long... maybe half an hour (your suggestion) is OK.
Also: I don't know; I haven't been playing [that / very] long... maybe half an hour.

Is that what I'm supposed to say? Other options? According to my previous post, "I haven't played long... maybe half an hour" should be ok too, but for some reason I believe most native speakers just choose the continuous tense for this meaning. You believe right. I haven't played long suggests to me: I don't have a lot of playing experience -- there are not many occasions on which I have played. Adding maybe half an hour seems to add something contradictory.

CJ