I activated my brand new 520 about 2 weeks ago. The only updates I saw was on the apps tile. It said there were 17. Most were small, a couple megabytes here and there. I only updated maybe 10 of them because I didn't use the other apps. I did each one individually, most only took a few seconds. But I did them at home using my router's wifi.
I also went to setting to do a phone update. I've checked it a couple times a week and it says my phone is fully up to date, I didn't need a phone update. I guess it was done at the factory. Maybe all new 520's are updated now?