I agree Masherbrum ... and he's got to be in his 50's ..
He'll be 59 in September bro.
He's kept himself in fantastic physical shape.
Neil is a rare breed of drummer and this is coming from a drummer of 14 years. After Presto he wanted to become more of a craftsman of his instrument. He went to Freddie Kruger (Buddy Rich's roommate IIRC) and started to use a "traditional grip". He wasn't ready to implement it by the time Roll The Bones came around. So after RTB, he switched and to this day, EVERY new song he uses a "traditional grip", while EVERY Pre-Counterparts tune is drummed "matched grip".
Also of note, he uses the "heavy end of the stick" facing outwards. But, to switch grips and be just as crisp as the other, is NOT as easy as it seems. I love Portnoy, but it's because of the former that Neil is possibly the Greatest Rock Drummer alive. Not to mention he writes the lyrics to every tune and doesn't even sing them (which is also difficult).