1. I've been playing volleyball for 2 hours.
2. Eric had been paying guitar for 40 years.
3. my sister had been living in Switzerland since 1997
4. we've been walking for two hours.
5. he's been sleeping since eleven.
6. Veronica has been driving a car for 8 years
7. I've been studying classical music since I was 16
since указывает на начало действия (с 1997, с одиннадцати, с тех пор, как мне было 11)
for указывает на длительность процесса (сорок лет, два часа, и тд)