How long do cycles of mania last in manic depressive disorder?

Manic. Bipolar cycles usually last an average of few weeks, with exception of rapid cyclers who can show mood shifts day in/day out.
I have seen . three to four months quoted for the average length of untreated mania. (http://www.patient.co.uk/health/bipolar-disorder-leaflet) However, please be aware that the duration can be quite variable. The DSM V duration definition of mania is: "lasting at least 1 week (or any duration if hospitalization is necessary"