Swan in his book, Practical English Usage, in 459.2, p.447 under the heading temporary or permanent says: "We use progressive forms mostly for shorter, temporary actions and situations. When we talk about longer-lasting or permanent situations we often prefer the simple present perfect"
Below you have to fill out the blanks by putting the verbs in the Present Perfect Simple or Present Perfect Progressive, and choose the latter where possible:
I ____ (go) on package holidays for years and I've never had any problems.
There is no more context to the sentence. The correct answer is using the present perfect progressive only (have been going).
My question is why the simple, and why not both? Does not "for years" and maybe the experience of many holidays, qualify the sentence for present perfect simple?
Another question is about a quote from a traveler who has been exploring the world since he left the university. Currently he is in Africa. He hasn't been feeling well for the last week. He said:
I've [tried/been trying] a lot of different foods on my travels and I've never had any problems before. But everyone has been looking after me very well.
At the end of the story, he said:
I have been exploring the world for over 15 years, but I've got a long way to go
The correct answer is the simple only (have tried) not the progressive. I have no problem with using the simple here but the question is why cannot the progressive be used? The traveler hasn't stopped exploring the world. He still has a long way to go, and probably try more foods.
The last question is about the form of the verb: explore (simple vs progressive). What is the [slight] difference between:
I've explored the world for over 15 years,
I've been exploring the world for over 15 years.
Swan in 459.2 p.447 says: "Progressive and simple tenses are sometimes both possible, with a slight difference of emphasis." He gave two examples but didn't male clear what the difference is. As an example, he gave: "Harry has been working / has worked in the same job for thirty years"