I've experienced both type of battery performances, two 920s with terrible batter life and one with good battery life.
You can put the blame on some apps, but I was able to restore my settings and apps from my original 920 that had major battery issues into a 2nd phone. THe 2nd phone battery life was great and could last me more than a day easily with the same exact settings and apps. After performing well, i pushed the 2nd phone harder downloading more apps, appsi didn't need and apps i did need with more apps running in the background and the 2nd phone performed just as good as basic settings. Now i get a 3rd phone, you may ask why i gave up my 2nd phone, i gave it to a family member bcause her phone bricked. So i get the 3rd phone, did a restore and not only did i get battery drain, now i get a rebooting problem with a phone that came with the "portico" update. An update that was supposed to rectify the rebooting issue.
So in my experience and my experience the world revolves around, apps had nothing to do with my terrible bad experiences, the phone itself was the issue.
5 of my immediate family members have 920s uincluding myself, 3 of them were defective. There is an issue with these devices, and coming from an iphone from 2007-2011 and never having to do a warranty exchange for them, i've experienced multiple with nokia's 900 and 920 within a year.
So it is true, it is like a lottery, the chances you get a good phone and a bad phone is not so different.