Sorry Kotfor - this is still wrong.
When we use 'in' followed by a defined period of time (the last 20 years, my entire life, all the time I've known you, etc) we are connecting this period with one or more specific events. These events could be expressed in several ways, such as 'only once' or 'very rarely' or even 'never'.
For example:
'In all the time I've known you, you've only been abroad three times';
'I've never eaten an oyster in my entire life';
'He only spoke to her once in the following week'.
As with so many rules, there is bound to be the occasional exception:
'In 20 years of operation, the factory turned out 3 million tractors'.
To express an action that continued from the beginning to the end of a period, you cannot use 'in' but will need 'for':
'I've worked here for the last 20 years'.
In the sentences you quoted:
1) I will say quite frankly since I have been here, in 5 years I have never heard of so many studies, so many reports, so many commissions, and so little hardware that really works.
2) I grew up visiting the area a couple of times a year but I haven't been here in 5 years.
3) Nothing has worked there in a long time.
4) John Smith hasn't worked here in four months.
5) “She hasn't worked here in a decade,” I said to Ives
No.1 is fine because of all the specific events listed, but the others are examples of ellipsis, ie: a word that would normally be used to complete the sentence has been left out, trusting the listener to understand it. In each of these cases, the missing word is 'once'. Even so, these sentences are of a colloquial nature, just passable for speech, but not acceptable in prose. For this you'd need to replace the 'in' with 'for', for the reason given above (ie: not at all, from beginning to end).
By the way, the first part of example 1 above is most awkward. There is either repetition or confusion, neither of which is good! If I'd been there for 5 years, I wouldn't have said 'since I've been here, in 5 years...' as that would be repetition. If I'd been there for 20 years, confusion results from saying 'in the last 5 years'. Why mention the previous 15? All too complicated. Just use one or the other.
Hope this helps, or have I muddied the water?:-?