A clean nose reduces the need for antibiotics. The current overuse of antibiotics for upper respiratory infections is the major cause of antibiotic resistance. Nasal irritants cause most allergies and are a major trigger of asthma. The common cold, which starts in the nose, is a major cause of time loss from work and school. Even the flu virus enters the body through the nose.
Childhood seems to be where most problems start.
Children and the people who deal with them, day care workers and primary grade teachers, should see the most benefit. People with chronic problems should benefit. If the CDC is correct, whoever washes their hands should wash their nose and this should be a benefit to most adults as well. It depends on how bad the problem is. Most of the time adults can get by with two sprays in each nostril twice a day.