Which of the following is NOT an advantage of bonding?

The reason "Easy up-do's" is not considered an advantage of bonding lies in the nature of the bonding process itself. Bonding typically involves using adhesives or bonding substance to attach hair extensions or pieces to natural hair. While bonded hair can create a voluminous and dramatic look, the method can complicate certain hairstyles, especially intricate up-dos. The added weight and potential restrictions from bonding may not lend themselves to the flexibility needed for doing various up-styling techniques effectively.

In contrast, the other options highlight clear benefits of bonding. Long-lasting results refer to the durability of bonded hair extensions, which can remain in place for weeks or even months with proper maintenance. A natural appearance is a significant advantage, as quality bonding can blend seamlessly with the wearer's own hair, creating a look that is realistic and aesthetically pleasing. Finally, less damage to hair is often cited since, with proper application and the right products, bonding can minimize the risk of damage associated with alternatives like braiding or clipping that place stress on natural hair.