* Your hair growth: As your hair grows, the highlights will move further down the shaft, creating a noticeable difference between the highlighted and natural hair. This is especially true for lighter highlights on darker hair.
* Your desired look: If you like the subtle blending of the highlights with your natural hair, you might not need to re-highlight. If you want more obvious highlights or a more dramatic change, you'll need to re-do them.
* Your hair type and color: If you have fine hair, the highlights may fade faster than on thicker hair. If you have dark hair, the highlights will be more noticeable as they grow out.
Generally:
* For maintenance: Most people need to re-highlight their hair every 6-8 weeks to maintain a fresh, vibrant look.
* For a complete color change: You might need to re-highlight every 4-6 weeks.
* If you're just getting highlights for the first time: It might take longer for your hair to grow out enough to need a touch-up.
To know for sure, it's best to consult with a stylist. They can assess your hair and advise you on the best course of action.