The only way someone can trade for 24hrs is via an automated, mechanical or intricate bracket order trading system.
In contrast, a discretionary trader (someone that's not automated or mechanical) couldn't do such unless he traded one day for 24hrs and then sleep the next day...alternating the trade then sleep days to prevent burnout within a few weeks.
Seriously, there are lots of traders that'll trade full-time the rth (open to close) and then a part-time (few hours) in the overnight trading session or vice versa.
When I was single (no spouse nor kids) I would trade the rth from open to close and trade about 1hr 30mins overnight in the Eminis around the time when Eurex futures open. However, I'm no longer single and such a schedule will eventually kill you (literally).
Thus, now that I'm a family man, I only trade rth from open to close but with lunch break and a few other scheduled breaks...I'm really only trading while glue to the monitors about 5 hours per day.
By the way, any job that causes a serious lack of sleep or insomnia...
You'll dramatically increase your risk of the following:
* Cancers
* Strokes
* Diabetes
* Heart Disease
* High Blood Pressure
* Heart Attacks
Simply, when the brain is resting less...the body is working much harder until it begins to stress. Yet, if you're in great conditions and 25 years or younger...your body can handle such a stressful workload for a few years without any noticeable health problems.
I've met a few traders in their early 30's that had to quit trading after surviving cancer, stroke or heart attack when the doctor highly recommend changing careers if they wanted to reach 40.
Mark