How long after frostbite do you know if it will heal properly?

Long Time. It can take weeks to months to fully recover from frostbite. How long depends on how bad the frost bite was and how much tissue damage occured. Watchful waiting is best as there is no good way to tell how much tissue was damaged early on in the recovery. If blisters or scabs have formed, let them heal on there own. Hands may be sensitive for a long time after frostbite.