Although there is no standard answer, a minimum of 3 months is a safe place to start. If minimal facial surgery with no breaking of bones is being performed than this time may be reduced to as short as 8 - 10 weeks if permitted by your facial surgeon. Glad to help.
The problem is the positioning after surgery. Butt implant surgeries require prone positioning for 2-4 weeks which leads to facial swelling-something that you don't want after facial surgery of any kind.There is no preset rule and every surgeon will have a different protocol. We treat a lot of transgender patients after facial feminization and have found an interval of three months minimum to be best.I hope that is helpful.