Last week I returned to Russia after an overseas trip and I went to Moi Dokument to register ( As an American Citizen I have a 3 year multiple entry private visa to Russia)

As I recall from the past after registration it was possible to stay in Russia for 6 months before having to leave (cross the border and return) again.
This time I noticed that Moi Dokument have made the registration for 3 months.

Does that mean I need to leave Russia before this 3 month registration finishes or is it possible to prolong the registration for another 3 months through MVD here in Moscow ?

If anyone has any knowledge / experience with this it would be helpful to know.

Thanks in advance!