I think they said bipolar. Nah not that I ever saw or heard.
Bipolar can often be progressive. I think it hits different in different people, but the one friend I know the best who has it, when he was younger he'd go 4-5 years without an episode and in-between those episodes (which lasted from a few weeks to a few months) you never would have guessed there's a problem at all.
Then around 25 it became an episode every 2-3 years.
Then around 30 it became an episode every year and in-between you could often see there was something not still right on a bad day or a bad time of day.