Mistress of Midlife Crisis performs at the Oceanside Pier Amphitheater for Operation Appreciation 2012, May 19. Oceanside Chamber of Commerce hosted the yearly event to promote the ongoing relationship between the Southern California community and the local military. - Mistress of Midlife Crisis performs at the Oceanside Pier Amphitheater for Operation Appreciation 2012, May 19. Oceanside Chamber of Commerce hosted the yearly event to promote the ongoing relationship between the Southern California community and the local military.