How long after breast reconstruction implants placed after 4 months of tissue expanders does the swelling go completely down?

Varies. Most swelling after surgery resolves by 6 weeks or so. However, a lot depends on what was performed exactly. Swapping out expanders for implants is usually quite straight forward. Sometimes more extensive surgery is required for the best results eg removing scar tissue, reshaping (internal, external, or both), fat grafting, etc. Your plastic surgeon will know best for your specific situation.
BreastReconstruction. In most cases swelling after breast reconstruction may persist to some degree for at least three months after surgery and may last for several months. Be sure to follow up with your surgeon as fluid collections around the implants may mimic swelling.
It can take a while. As long as you are not having any complications such as fluid collection, delayed healing or infection, then the swelling should improve spontaneously but it can take months. Check with your surgeon to be sure that you are healing on schedule. It is best to resume all activities and exercise as soon as tolerated to help with your recovery.
Usually 9 months. I typically inform my patients that it will take somewhere between 6-9 months for the vast majority of the swelling to resolve.