The problem isn't so much the number of hours you work, it's more a matter of if you enjoy them or not.
I was a SysAdmin for years, during which time I worked 50 hours on a *short* week. A typical week was closer to 70, and I had on many occasions done in excess of 100. I had to take a laptop with me when I went on my 3-weeks-after-10-years vacation to Arizona in January (Arizona in January sure beats Ottawa!). I ended up working 1 to 2 hours a day while on "vacation". Every damned day.
I hated my job, but I was too busy to look for another one.
Then I got cancer, and lost my left kidney. (Well, I didn't _lose_ it; the surgeon took it out, sent it to the Lab and the report came back "malignant'). As part of my recovery, I was *forbidden* to lift anything heavier than a 10-pound bag of sugar, *required* to have a nap for at least 1/2 hour a day, and it was suggested I find a less stressful lifestyle. I was basically confined to the house for 6 weeks. The after-effects of the anasthetic left me unable to concentrate on much of anything for more than a few minutes at a time. I could read the newspaper's comic page, but that was about it.
There's a lot to be said for a short nap in the afternoon. All of it positive.
When I was able to go back to work, I could handle it, but now the 100-hour weeks annoyed me. So, I quit SysAdmin-ing (I don't think that's an actual word...), and now work as Tech Support for a much smaller firm. I do on-call sometimes, but mostly I get to do a 40-hour work week.
Eliminating stress _does_ make a difference. I've noticed it. My wife's noticed it. My son and daughter-in-law noticed it. I get fewer cold/influenza bouts, because I'm not so run down. I _swear_ I'm wiser now, but that could just be because I'm alive (and therefore older) and appreciate it more.
If you aren't happy with what you do, it'll kill you, regardless of the hours/days/weeks schedule.
If you enjoy what you're doing for a living, the amount of time spent doing it doesn't really matter all that much.