I started light boxing at 9 months, but by light I mean LIGHT. Just getting the right rotation on the hip, driving through the bag was a project to get into. I wasn't hitting the bag with authority with hands until about 12 months. Pad work I didn't do as much, but it's no problem now at almost three years.
You know your power for boxing comes from the hips, so they have to not only be strong, limber but also have to support the impact. If you're at that level, you'll be generating a respectable amount of power from your hips, you want not only the hip device but aso the smaller supporting muscles that are cut or moved to support the movement.
All of that needs to recoup. I wasn't hitting the bag with authority until fourteen months, basic kicks - front, round and eventually the side kicks.
That was me. Others may have different experiences, but the process is not really muscular at first (except for the smaller muscles), but structural. Your device has to set, get the bone grown into it, the bone grown strong and the lost blood flow to the femoral neck restored before you can push the muscles to get back.
You also will need to retrain the muscles to do actions that are now instinctual. Once they're trained they get back fast, but you'll find some unusual lack of coordination that needs to be overcome.