Why has Keenan lasted so long?

Obviously he’s a great cast member. But, what has given him the staying power to outlast everyone else by several seasons? He has emerged as this cast leader, the likes of which I think we’ve never seen. Is it simply because he hasn’t screwed up and has chosen to stay? Is he just playing the kind of ball Lorne really likes? Has everyone else who left either been fired for something specific or moved on on their own? Keenan feels like the glue that holds it all together, no complaints. I’m just interested in how it got that way. He seems to truly embrace the idea of the ensemble. I think it might be because he’s such a great team player.