How long should I keep my tape in place to reduce scarring?

The surgical tape applied after surgery helps keep the incision approximated - making the scar heal nicely. At three weeks If the tape is dirty and falling off - I would recommend removing it. At your next appointment you can always have it replaced. I recommend my patients keep the tape on for at least 4-6 weeks - Replacing it at each follow up appointment. 

Thank you for your question.  Generally steri-strips (the white or tan tape put on the day of surgery) is either removed by 1-2 weeks (skin has healed enough by this time) or some surgeons let it fall off on its own.  I generally don't like to have bloody or goopy tape on nice incisions, so I have patients remove it.  Silicone tape is often then used weeks out to help the scar remodel.  This is often used for 3-4 months to help the scar mature.  

You should follow the instructions of your own plastic surgeon relative to tape on the incisions. Scientifically speaking there's no evidence that this has any long-term benefit.