I've read conflicting reports about whether or not bipolar symptoms worsen over time. Some scientists say the symptoms worsen and we suffer a general cognitive decline.
Some say it happens to unmedicated bipolar people due to stress on the brain from extreme mood swings over time. But some scientists maintain that none of those theories are correct.

It's hard to know what to believe.

Let's just hope in your case, your good mood is something positive and something that will last.