The present perfect progressive tense has several
different uses. One is very similar to a common use
of the "normal" present perfect tense: showing an
action that began in the past and that is still continuing
now. When the present perfect progressive is used
in this way, the emphasis is on the length of the
continuing activity. In addition, use of the present
perfect progressive often suggests that the action
has continued with no interruption from its beginning
until the present.

For this use of the present perfect progressive, the
"time words" for and since are very commonly used:

Joe has been studying at State University
since September.

The baby has been crying for a long time.
What's wrong?

I've been driving since daybreak. I'll have to
stop soon, I think.

Other "time words" are also commonly used with
present perfect progressive--in particular, all + a period
of time:

It's been snowing all day. When will
it stop?

She's been studying all morning. I'm sure
she'll take a break soon.

I've been thinking about Bob all week.
I really miss him!

We've been trying to reach Sara all afternoon.
Where could she be?

To add even more emphasis to the idea that the action
has been uninterrupted, the set phrase the entire ____
is sometimes used:

It's been snowing the entire day and there's
no end in sight.

She's been studying the entire morning. She'll
have a headache if she doesn't take a break soon.

I've been thinking about Bob the entire week.
I hope everything's OK with him.

We've been trying to reach Sara the entire
afternoon. Are you sure she's at home?

_______________________________________________

Special Note:

All of the example sentences above could also be written
with "normal" present perfect tense, but if they were, the
feeling and emphasis would be quite different: there would
be much less of a suggestion that the action was uninterrupted