Which factor is NOT considered when customizing eyelash extensions for a client?

When customizing eyelash extensions for a client, the factors considered typically include the client's natural lash health, eye shape, and their desired look and style. Each of these elements plays a crucial role in determining the appropriate type and length of extensions to use, ensuring optimal results and maintaining the health of the natural lashes.

The client's natural lash health is vital as it informs the technician about how much weight the natural lashes can handle, ensuring that the extensions do not cause damage over time. Similarly, understanding the client's eye shape helps to create a look that enhances their features and meets aesthetic goals. The desired look and style guide the selection of materials, lengths, and curls to achieve the client’s vision, allowing for a personalized experience.

The client's schedule, while important for overall appointment logistics, is not a direct factor in the customization of the eyelash extensions themselves. This aspect might influence when the client should come in for maintenance or how frequently they can have their lashes applied or filled, but it does not impact the technical choices made regarding the extensions during application. Therefore, it is appropriately identified as the factor not considered in the actual customization process of eyelash extensions.