As we see that cpc sydney too transfers files and it happens within few days for some people and few weeks for some people hence i doubt that we get much delay just with transfer of file due to address change.
Its all about the local office how it handles the files and officer how fast(if) (s)he works on it. But if one is waiting for 20 months then surely one can take chance with new office since nothing happened for 20 months hence what more delay it would add with few weeks.