Final answer:
Clients should return to the salon/spa for a facial treatment every 4 weeks for healthy skin maintenance and stress reduction.
Step-by-step explanation:
For healthy skin maintenance and stress reduction, it is recommended that clients return to the salon/spa for a facial treatment every 4 weeks (b. 4 weeks). This frequency allows for consistent care of the skin and enables the esthetician to address any specific skin concerns or changes that may arise. Regular facial treatments can help maintain a healthy complexion, improve circulation, and provide relaxation benefits for stress reduction.