Season. Period. I'd make it lifetime if I thought that was even remotely likely.
Two words for you. Repeat offender. Get this guy out of the game.
The comparisons to hockey are laughable. In the NHL you get 5 minutes for breaking out into an all-out fist fight. In the NBA, you get a suspension. So take the hockey "25 games" template and correct on that scale. The NBA is not supposed to be a violent game.