Was actually thinking about the same thing… Especially the ‘it could take days’ part.
It’s currently busy since 3 and a half days or something, still not calmed down and both my Twonkey + NAS are saying it’s updating the database.
In addition to this, I made this topic a few days ago 
http://community.wd.com/t5/WD-My-Cloud-EX4/Media-Server-updating/td-p/709610
Fun part is, with all the luck on my side I just took a look and my NAS now says;
Music Tracks:0 Pictures:0 Videos:0
While it’s been busy over 3 (and more) days of scanning/building/whatever…
Rescan/Rebuild didn’t do anything and when I look at my Twonkeypage it didn’t help me either… Great stuff 
