The correct form of present perfect...

[Mehrgan]

Hi,
I was wondering if any of the following sentences was ungrammatical or less idiomatic.

'It's 4 years I've been working on this model.'
'It's 4 years I'm working on this model.'
'It's been 4 years I've been working on this model.'
'It's been 4 years I'm working on this model.'


In this case please let the 'it's 4 years' part remain at the beginning of the sentence. Thanks in advance.
(I suppose, the second parts are all correct, but in the case of the 'present perfect continuous' it could suggest the model has been completed. Is that right?)

[emsr2d2]

Hi,
I was wondering if any of the following sentences was ungrammatical or less idiomatic.

'It's 4 years I've been working on this model.'
'It's 4 years I'm working on this model.'
'It's been 4 years I've been working on this model.'
'It's been 4 years I'm working on this model.'


In this case please let the 'it's 4 years' part remain at the beginning of the sentence. Thanks in advance.
(I suppose, the second parts are all correct, but in the case of the 'present perfect continuous' it could suggest the model has been completed. Is that right?)

They're all a bit clunky, to be honest. The most likely versions (if the model has not been completed) are:

It's been four years since I started working on this model.
I've been working on this model for four years.

If the model has been completed, then:

I worked on that model for four years [before I finally completed it].
I was working on that model for four years [before I finally completed it].

[shabani]

And would you please explain if its clunkiness necessarily makes it wrong or if native speakers use any of these by mistake? which one makes more sense?
And what about questions like:
'How long is it you're teaching?'
'How long is it you've been teaching?'
I think I've heard this type of questions beginning with is it and followed by another tense.

[Raymott]

And would you please explain if its clunkiness necessarily makes it wrong or if native speakers use any of these by mistake? which one makes more sense?
And what about questions like:
'How long is it you're teaching?'
'How long is it you've been teaching?'
I think I've heard this type of questions beginning with is it and followed by another tense.

To me, all of the original sentences are wrong, and so are yours. Sorry.

[5jj]

'How long is it you've been teaching?'

I wouldn't call that actually wrong, but it isn't natural. We'd be more likely to say:

How long have you been teaching?

Or possibly:

How long is it that you have been teaching?
How long is it since you started teaching?