would you do that?

We're opening a new retail outlet soon, and I'm the new store manager. Since it's a new opening, the company is still looking for employees. Finding the right staff is proving more difficult than expected. I've been thinking about talking to my supervisor tomorrow if he pays me €800 more per month, so he'll essentially hire one less part-time employee, which would mean I'd work 12 hours a day instead of 8. The job isn't physically demanding; it's more mentally demanding, if anything.