Greetings!
Question: How long have you been studying English? I've been studying English all my life, for many years, since I was a baby!
The above is an example of the use of the present perfect continuous tense using time phrases, such as, "all, for, and since".
There are some very clear uses of the present perfect continuous for ongoing activities that started in the past and continue into the present, they have an unspecified start date and continue in the present.
As with the present perfect we use "all, for, and since" to create time phrases.
Here's a good explanation of the present perfect continuous, also called the present perfect progressive, with exercises from a website called Perfect English Grammar:
http://www.perfect-english-grammar.com/present-perfect-continuous-use.html
Enjoy!
Bonnie
