I completely fail to see the inevitability. People don't fall into a coma the minute they leave the office. If he's grinding away 5-6 hours extra hours alone in the office every day, while you're spending those 5-6 hours meeting new people, hanging out with friends and colleagues, learning new things and playing around with fun hobbies and projects, why should he grow more than you.
It's just as likely that two-three years down the road he'll be completely burnt out with a stagnant skill-set while you have a great network, varied skill-set, plenty of energy and are ready and able to use those to move onto bigger and better things.
Besides you can train your biological cycle to do wonders.
Edit: If it's the money you're after I think you should try to work smarter not harder :-) i.e. if you're only way to get more money is to work more hours maybe you should find another job or change career.
So as long as you are happy with whatever you do, you are the happiest man in the universe.
And I have no problems with this.
I have problems with people who stop other people from working hard, just because they don't want to.
He and you do your day job in 8 hrs. But he puts in an additional 5-6 hours a day and is likely to put for the coming years.
Now suddenly you will find yourself in a corner as he will grow(in comparison) inevitably. And there will be little you can do.
Putting in crazy hours isn't mandatory, but neither is winning and succeeding.