Past perfect continuous

Look at this example:

Before Jimmy finally could pay the journey to Thailand, he had been working for months.

Jimmy now is on holiday, he paid his holiday one month ago.
He had to work for a long time before i could pay it.
This action of working, doesn't continue till now, but it stopped when he paid in the past.

The Past Perfect Continuous is used to show that something started in the past, and continued up until another time in the past.
How is composed:

more examples:
- When the kids came into the house, is was quite clear to see from the dirty clothes that they had been playing in the garden.
- I had been waiting for Susan for 2 hours when she arrived

Let's focus on these sentences:
- Jason was tired because he had been jogging.
- Betty failed the final test because she had not been attending class.

And now compare the examples above with these similar examples in the present perfect continuos. 

The only difference is that these examples are referring to the present:

- He is tired because he has been exercising so hard.
- I think I'll fail this last test because I haven't been studying at all.