Are you referring to the actual scan or the fact that it keeps spinning?
If there’s new files added, Plex will be quite busy detecting intros of those episodes – this will take quite some time, even if the files themselves have already been added and downloaded all metadata.
You can move the detection of intros and the generation of preview thumbnails into the server maintenance period.
Which of course means these will be only available with a delay of ~1 day.
But the speed of library scans will be as it was before these features were introduced.