I like to backsweeten at the beginning of the aging process. The "raw honey" flavor never fully ages out, but it does tend to mellow with time. I generally pull a sample, and prepare a range of samples (1.010, 1.020, 1.030 or 1.010, 1.015, 1.020, etc.) Sometimes one is perfect, and sometimes I need to do a second run in a narrower sample range.
Once I find the right level I will scale it to the full batch. I generally add it while racking to tertiary and let it age after that. If needed, I adjust the acid level after backsweetening.