It seems that the Portuguese capital offers customers shopping until midnight in September. I remember when I lived in Rua de Sao Bento, once a year for three nights this street's antique shops were open until midnight. People would shop for antiques while seeing special performances such as dancers and singers.
Maybe because of this tradition, the shops in Avenida da Liberdade, Rua Castilho and Chiado will be open on 9 September from 7pm until midnight. According to Follow me Lisboa, shops will offer competitive prices together with lots of entertainment.