Manic episodes can occur even in Bipolar-II, just less severe than Bipolar-I's. Plus, there are so many variations and time lapse(s)/intervals between episodes.
Some people can go on episode free if one follows a treatment plan including taking mood stabilizers, and of course keeping in touch with the prescribing pdoc of any changes in mood, doing so can help stave off an oncoming episode. Good, strong, communication with pdoc and/or therapist is so very important to achieve progress.
More than one disorder (DX) can happen in a person, whilst some are mistaken for one or an other by symptoms that often mimick various disorders, so unfortunately some pdocs can mis-diagnose a person, thorough evaluation(s) are most necessary. As changes become apparent, a re-evaluation should be done or an evaluation from a different pdoc.
I wish I had some info. that may be of help to you, but please allow me to stress, Bipolar disorder is NOT a "life sentence", with treatment,communications,consistancy, and co-operation by you besides your pdoc, things can work just fine.
Please take care now,
DE