I know that adverbs of frequency such as "often" are usually put before the main verb (or after if the main verb is "to be") or at the end of the sentence. Examples:
- I often walk on the beach / I walk on the beach often.
- I will often run on the beach / I will run on the beach often.
- I am often angry with my students. / I am angry with my students often.
However, I am not sure which verb is considered the main one in sentences with "used to" and therefore I am not sure of the position of "often" in sentences with it. Which one of the sentences below is more usual?
- I used to often go skiing in the winter.
- I often used to go skiing in the winter.