What is the longest period of either depression or mania that people experience?

I feel like the first manic episode I had lasted a few years before I crashed into depression... and then long period of normalcy. The mania was probably hypo. And now I feel like the same thing has happened... my behavior is so different compared to how I've been acting for the last 4 years. Extreme enthusiasm, projects galore, followed by anxiety due to getting into various troubles, volatility, emotionally shutting down, impulses out of control. I don't do those things now .. and I didn't act that way before the point at which I think I went manic leading to current problems.

Anyway.... just wondering if other people have experienced this longer term stuff.