Well I really like @Barrie's answer most as always. He is sharp as always, put it simple and clear. Although I want to add some more information. You have pointed out the difference that Past Perfect Simple wants result and the Past Perfect Continues imply on continuous activity with unclear result. That is really important and all the people that have done it clear are rewarded +1 from me. What they have missed are the corner example and exceptions. So I want to make it clear- there are a list of verbs that do not have continues (Progressive) form.
Mental and Emotional States
believe, dislike, doubt, imagine, know, like, love, hate, prefer, realize, recognize, remember, suppose.
appear, hear, see, seem, smell, sound, taste.
agree, astonish, deny, disagree, impress, mean, please, promise, satisfy, surprise
be, belong, concern, consist, contain, cost, depend, deserve, fit, include, involve, lack, matter, need, owe, own, possess.
Sam has been having his car for two years. (Not Correct)
Sam has had his car for two years. (Correct)
Although some of them can be used in Continues tense with different meaning.
feel = 'have an opinion' - He feels he should get a second chance.
see = 'understand' - I see what you mean.
think = 'have an opinion' - I think we should leave immediately.
appear = 'look like' - That appears to be stale.
look = 'seem' - It looks impossible!
taste = 'have a taste' - That tastes yummy!
feel = 'feel physically' - I'm feeling awful this afternoon.
see = 'visit' - She's seeing a doctor this morning.
think = 'use the brain' - He's thinking hard about the problem.
appear = 'be on stage / perform' - Jack Daniels is performing at the Paramount tonight.
look = 'stare at' - I'm looking at that strange man.
taste = 'use the mouth' - The cook is tasting the sauce!
Remember that the Present Perfect Continuous has the meaning of "lately" or "recently." If you use the Present Perfect Continuous in a question such as "Have you been feeling alright?", it can suggest that the person looks sick or unhealthy. A question such as "Have you been smoking?" can suggest that you smell the smoke on the person. Using this tense in a question suggests you can see, smell, hear or feel the results of the action. It is possible to insult someone by using this tense incorrectly.
I am not quite sure, but I think that already, by the time, ever, never can be used only with Past Perfect Simple, because they are asking for result.