I discovered the source of my battery drainage problem, though it was quite by mistake. And TheBigNewt was right. Radios use up the batteries, not the OS.
It's not fun being a newbie.
Anyway, I found that I still had BerryTunes installed on my BB. I didn't even see BerryTunes on my BB while I had OS 5.0 installed (I don't really use it that much) -- it didn't appear as running in the background, it was just an icon in a folder so I didn't really see it and never uninstalled it along with the other apps I removed. I just don't use it that much and didn't think about it.
After downgrading back to 4.7, I tried to run BerryTunes but it kept rebooting my machine. So, I uninstalled it. Then I attempted to do a backup which failed on the device memory section over and over again. It seemed something had corrupted my device memory because I just could not complete a successful backup. I remembered TheBigNewt's post saying radios use up the battery, so by that point I figured I should reinstall OS 5 without BerryTunes and see if I could get a clean install -- what did I have to lose since I couldn't complete a successful backup of 4.7 anyway?
Sure enough, I completed a successful upgrade of OS 5 and there is no more battery drainage issue. Thanks to TheBigNewt for his post because it jogged my memory when I started having problems with BerryTunes after reverting back to 4.7. It must have caused some kind of corruption. (Oddly, it still didn't drain the battery after going back to 4.7 -- it simply wouldn't run at all).
I hope posting this doesn't upset anyone -- I knew it couldn't be the OS itself since it only seemed to affect a few people with battery problems. I thought it only fair to report back what the problem really was, and how it reinforces the position that it has to be something else on the device.
The only question I have now is, how do you possibly know what apps to install when you have these kinds of problems? You never know which one might throw everything off after an OS upgrade and cause you to spend more time than it's worth to resolve them?