[susan53]

The perfect basically has three uses :

1. to describe events which are true in both the past and present. Here there is no difference between the simple and continuous forms : I´ve lived here for 3 years = I´ve been living here for three years

2. to describe past events which take place in a past to present time frame (this week, today etc). Here the simple suggests a completed event and the continuous and on-going, unfinished event : I´ve read "War and Peace" this week vs I´ve been reading "War and Peace" this week.

3. to express past events with a present result. Here the simple suggests a single action, whereas the continous suggests repeated actions : I´ve cut my finger! vs Someone has been cutting pictures out of this book. You can see the difference clearly if you convert the first example to the continuous : I´ve been cutting my finger. Notice here that it is a meaning distinction, not "grammar" - someone who was masochistic, self harming or completely mad might well do and say it. Most of us wouldn´t.
This one is tricky though because sometimes the "repeated actions" can be seen by the speaker as a single event, and s/he will therefore choose the simple. Compare I´ve cut my nails (seen as a single completed event) with I´ve been cutting my nails (seen as completed, but as a repeated sequence of actions).

As ever, the grammar gives us the opportunity to make meaning distinctions. Which meaning you wish to express is up to you.