In my opinion I'd say bout half a year because people would not understand why or what made you do it . also people would be curios because if you haven't done that before why would you want to do a crime when you can't do the time.
Too general a question to answer with any specifics. It all depends on the wording of the laws in your state or jurisdiction (e.g.- Was is a business place? Was it a residence? Was the residence...
Robbery is a violent felony for which you can face 15 years to life in prison, depending on whether a weapon was used or displayed, if anyone was hurt or killed, and how much was taken.