First check the Arduboy specifications to see what microcontroller it uses:
8-Bit Microcontroller, ATmega 32u4
Then get the datasheet for the ATmega32U4:
http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-7766-8-bit-AVR-ATmega16U4-32U4_Datasheet.pdf
You don't even need to dig, it's right on the front page of the datasheet:
Write/Erase Cycles: 10,000 Flash/100,000 EEPROM
So you can upload 10,000 sketches to your Arduboy before you've exceeded the rating of the flash memory.