How long does it take a surgical incision to heal?

It depends: On if you mean for complete remodeling and for the wound to look the way it is going to stay- in that case at least 1 year (some say up to 2 years). If you mean for activity, this depends. If it's a small lac on your chin for example- could get back quickly, if abdominal surgery- at least 6 weeks. Keep in mind if you smoke, have diabetes or other anti-healing diseases healing will take longer.

4-6 weeks: At 4-6 weeks 90% or so of the strength in the incision has healed. The wound will continue to modify for the rest of your life. Thus scars fade with time.