How long after a laparoscopic appendectomy can a 38 year old male firefighter return to full duty?

Within 2weeks. Laproscopic incisions normally heal within 2weeks to resume normal duty.
Listen to your body. Complete wound healing doesn't occur for approximately 90 days, now no one stays out of work for 90 days. The wounds reach their maximum strength (burst strength) in 90 days. That will be 80% of the original strength. In my practice I tell patients to go about their daily activity as they would with the exception of their core. No lifting pulling pushing or shoving >40 lbs the first mo then.