After you create a blend shape, you can delete the target objects to free up memory and improve the performance of Maya. When you delete a target, the blend shape node keeps the target deformations in memory and the target slider deforms the base as if the target remained. The object is removed.

You save the most memory when you have complex targets that have only a few components that have moved slightly from the base. For complex targets that have many components moved from the base, you save the least memory.

Don’t delete the targets if you want to modify their shapes or remove them from the blend shape. Remember that when you modify targets, Maya updates the resulting blend shape.

You can delete the object manually from your scene, or you can have Maya delete the targets when you create the blend shape.