How Long Will Fat Transfer to Pecs Last?

When fat cells are transferred to another area, some of the cells die, always! There is never 100% take as the new area must provide oxygen to the fat cells so they live, before new blood vessels grow into the area supplying them with oxygen.  The fat grafting / fat injections / lipo-transfer / lipoaugmentation procedure can involve a series of treatments, each building on the prior treatment's success. Once the fat cells live, they may live for many years in their new environment.  You should not think that fat injections are temporary, although no guarantee can be given that they will last long term.
 

There is always some volume loss after fat transfer as not all the cells can survive.  The contribution of stem cells in not understood. Your pectoral volume should become stabilized after a few months.  Further injections will be needed if you need more volume.

Fat transfer is permanent once the fat has established its own blood flow. It is possible to remove the fat to make you more symmetrical but it needs to be physically removed which is complicated by the fact that fat is in your pecs. This is not an easy problem to fix. Sorry! Visit with a board certified plastic surgeon.