I had only one episode, it lasted 18 months of complete inability to perform my job (that I was perfectly capable doing before). Full recovery took several years. It was like a firecracker went off in your head and left a buzz that prevents you to stick to your task even for a second - except there's no actual buzzing sound.
The trajectory that took me there was acutely unpleasant but I would not describe any of it as boredom. You ain't getting bored on your death march.
Can't imagine several such experiences, I'd rather change career.
