If you have temporary extensions such as the halo hair extensions or clip ins extensions then no, do not sleep wearing your hair extensions. They will become tangled, matted and may damage your natural hair. Remove them, brush them gently and store in a cool dry place.
When you sleep wearing your permanent hair extensions you will want to secure them so that they do not become tangled. Braiding your hair before bed is a great way to prevent tangling and maintain your waves! Otherwise twisting in a top knot, or wearing a scarf are other effective ways to take care of your hair.