There are administrative rules that can support their Company is open more hours then Mon.-Sat. Office workers have different classifications: Exempt Employees, those individuals whom are paid a Salary may work +40 hours per week and receive no overtime or holiday pay. (they maybe on call for breakdowns or other problems...if they the need arises. Or, waiting on their own Business to experience Growth before scheduling this position full time.). For all practical purposes, when things go well they wont need to work. However, they may need to if the need arises.
*Keep your dialogue promoting your concerns...FRIENDLY.
I agree 100 % those companies will always pressure you to work extra hours however the moment some incident occurs they'll deny everything so bottom line is don't work beyond your legal hourly limit. Bottom line is don't drive illegal hours