Frequent supply switching for a microcontroller
I would suggest a small resistor in series with the Vcc to the MCU (maybe 10-100 ohms- chosen to drop perhaps 50-100mV in normal operation) and a capacitor in addition to the usual bypass capacitor of perhaps 100uF. You may need to add a bleeder resistor or a diode across the resistor to get the supply voltage to drop fast enough that a brief release of the pushbutton is recognized, depending on your circuit. This will help prevent any ESD from fingers on the switch destroying the micro. There is not really any other risk to the life of the micro from switching it on and off. 

Functionally though, I would strongly suggest that you enable BOR and consider using an external supply supervisory chip (reset chip). This will help prevent EEPROM corruption. If you're not too concerned about the odd fault, the internal BOR is probably fine.