How Long After a Full Facelift, Can Fat Transfer Be Done?

I doubt there is any scientific literature that addresses this directly.  With that said, one should wait a min of 3 months to inject into a plane that was created and needs to heal.  You can inject as early as 1 month (perhaps earlier) into areas that were not incised/elevated.

I generally advise patients to wait about 3-6 months after a facelift before they undergo a fat transfer.

You should probably wait about 3 months or until swelling has resolved. Find a plastic surgeon with ELITE credentials who performs hundreds of
facelifts, necklifts facelift revisions, and facial procedures each
year. Then look at the plastic surgeon's website before and after photo
galleries to get a sense of who can deliver the results. Kenneth
Hughes, MD Los Angeles, CA