How long is too long at work?

How long can you legally work before someone has to relieve you? like in a chain 24hr convenience store. I know that some places have prefrences as to their policies, but are there any laws against working so many hours straight without breaks or relief before it becomes too stressful, hazardous or inhumane even? I know there are child labor laws about you cant work more than say 30or 40hrs a week or after a certain time at night if you are under 18 and still in high school or whatever, but are there any adult labor laws like that? I know what I mean, does anyone else.....So very tired.....Thoughts extremely jumbled...

I live and work in Texas.

Every state has their own laws, although there is a federal minimum. you are entitled by Federal law to receive a 10 min break every 2 hours, after 6 hours you are entitled to 30 min lunch break then another 10 min break for every 2 hours worked after that. There is exceptions though for certain industries not retail though. As far as an hourly minimum in a day, I am not sure if there is one. You do have to have 8 hours in between shifts though by federal law. So if they make you return to work without a 8 hour break in time that is illegal. If you are being forced to work outrageous hours get a new job!

oh yess there is. by law you are to recieve at least two 10 min breaks and a 30 min lunch within an 8 hr shift. or at least a 15 min break and a 1 hr lunch in a 9 hr shift. If you know anyone going more than four hours without a single break they can sue there employer. Call a lawyer they have a big lawsuit on there hands

best quality work now just need 40 hours and vacations
otherwise you won't work longer than 50. You will die soon.
don't get in heavy debts. A lot people just work to pay them
and then they just live to work. Don't fall in that scheme. or don't be so american
what is the best?

It depends on the state. In Arizona, I believe, it's 20 hours before an 8 hour break, but it's been years since I've looked at the laws.