Does your cat shed hair excessively?

We have a Manx named Tabitha. She is 13 1/2 years old. She sheds hair like crazy all the time. She has done this since we got her four years ago. We used to brush her a few times a week, but she would still shed hair.

When we have time to brush her every day, it obviously helps more. When we don't, cat hair gets all over the house. We are constantly dusting and vacuuming.