Old acne scar treatment: ① 1–5 years old: respond similarly to recent scars, ② 5–10 years: 30–50% more sessions needed, ③ 10+ years: still treatable, 50–70% more sessions, ④ all ages: combined needle RF + subcision + pharmacopuncture works best. Old scars have more established collagen disorganization and require longer collagen remodeling. Patience essential — even 20-year-old scars improve significantly with proper treatment. Realistic expectation: 50–70% improvement, not 100%.