How long should it take for a tfcc injury 2 completly heal?

Depends: Depends on the exact injury. As with knee meniscal injuries, there is varying blood supply and thus varying capacity for healing depending whether it is a peripheral or central injury. Likewise how extensive is the injury. And was it derided or repaired. Was the radio-ulnar joint de-stabilized i.E how severe was the injury. So need to know more. Many do quite well.

2 - 3 months: Stable minor sprains in the tfcc can get better -- usually about 2, maybe 3, months. Unstable sprains or out-right tears usually need a surgery. From surgery, it is reasonably also 2 - 3 months. These can heal and can get better! it takes a good diagnosis and proper treatment by the doctor, and patience from the patient!

It might not: TFCC injuries are difficult problems. Since the injured tissues don't have a direct blood supply healing is slow (possibly months) and might not be complete. If you have problems beyond a couple of weeks your should see a hand surgeon for evaluation. Long-term an unhealed injury can lead to wrist instability and degeneration.