Mike has always been comfortable with who he is, which makes him pretty reliable, and also means that he never sang anything really that was too much of a stretch for him. He'll sound good forever. He has better days than others though, I've seen sometimes when he seems like he doesn't have much strength, but I think that may actually be him not exerting himself too much, lol. He could probably still sound almost the same in the studio. He's really into T.M. apparently though, so I think he'd rather do everything soft and meditave than swagger like he did when he was young.
On youtube just to the right they have this killer clip of Carl absolutely murdering the song, miss that guy.
http://www.youtube.com/watch?v=eGVbkPhGFHQ&feature=related