Hi,
it depends. Auto trim afaik writes a change to the trim memory every second (if not interrupted), then 'listens' to the sensors, then makes the next adjustment.
So if there's not much to do, it will be a quick run, if there's more to trim, it might take a bit longer.
Usually, if you have (combined) about one minute of trim flight state, all should be well.
If you bring back the model, if it drifted too far, you interrupt, if you do a control pirouette, you interrupt, but that doesn't really matter, it does not reset the trim.
Also if you already did a trim flight, if you made some changes on the model and want to re-do it, it will start/continue with the already learned trim values (unless you clear the trim values, then it will start from zero).
Kind regards
Eddi
Born to fly ...
forced to work.