'often go together to the movies' should also be acceptable. I have reported this
It feels more natural to put "often" before the verb
Anna ja Hilla käyvät yhdessä elokuvissa, without the word often=usein, means that they go to movies but not so often. It's based on the context, dont put "usein" in every verb, because that means you do it a lot.
I know it is frowned upon in formal English to split infinitives but in ordinary conversation it is often done. N.B. I did not say ' it is done often' which would be more formal.
It is only frowned upon by aging prescriptivists, but modern style guides agree that to boldly split infinitives is definitely okay!
A gentle correction. It is not a split infinitive. In this case "to" is acting as a preposition, not part of the infinitive.
Like others, I wrote "often go together to the movies," and it was marked wrong. Reported.