Question: How do you know you'll need to replenish your staple supply?
Option 0: Mark one end of 20 or so staples with a red sharpie pen. Load them so that red ones will be used at the end. When your stapler starts punching red, you need to buy staples.
Option 1: Mark one end of 20 or so staples with a red sharpie pen. Load them so that red ones will be used at first. When your stapler starts punching red, you need to buy staples.
Answer: 0