My experience through various sectors of the software industry (including gaming) is that virtually nobody really works 9 am to 11pm for months. But some people are happy being at the office from 9 am to 11 pm assuming the "work day" includes a multi-hour team lunch break, some random breaks for playing Doom II, Diablo 3 or the newest Battlefield or whatever is hot at the office, lots of slashdotting/redditing/HNing/etc, hours long discussions about what happened on the hot geeky tv show, etc. So what it comes down to isn't even the workaholics vs the non-workaholics, but the totally tech-focused geeks vs the people who have non-tech things going on in their lives.
FWIW, up until my early-mid 30s I was very much the former, so I don't entirely begrudge that lifestyle, but I think it is mostly fantasy that those people are putting in significantly more actual work hours than the other group. Personally, I know I'm vastly more productive putting in 8-ish hours day now than I ever was when I was putting in 16-ish hour "work" days, though everyone's mileage may vary.
That said, there was lots of downtime, mainly for people whose brains were burnt like mine. Never multi hour lunches though.
It would be surprising if on a talented team there simply weren't people who had much more stamina than others, or just enjoyed their work much more. I'm not saying there's something to be glorified or emulated there.