Ответ:

for

They study for two hours every day.

They are studying for three hours today.

He has lived in Bangkok for a long time.

He has been living in Paris for three months.

I worked at that bank for five years.

Will the universe continue for ever?

We do not use for with "all day", "all the time":

I was there all day. (not for all day)

since

He has been here since 9am.

He has been working since he arrived.

I had lived in New York since my childhood.

It was a year since I had seen her.

How long is it since you got married?

She's been on the phone for hours.