How ong would it would take for a mastectomy to heal?

Varies. In a routine mastectomy with no immediate reconstruction, the skin will be healed in about 7-14 days, and closure staples may be removed. However, healing will continue for up to a year. So a final cosmetic result will not be immediately seen. The entire process changes if there's immediate reconstruction with tissue flaps or expanders. Your activity will be limited for about a month. Good luck.