If you really want to find out what is keeping your phone's processor awake and chewing through your battery, look no further than BetterBatteryStats available for $2.89 in the Google Play Store. Install it. Run it.
When you open the app, you'll see a screen like this
If you are seeing a lot of overnight activity or want to view what is happening during a specific time period, BBS includes an option to address this. Go to Menu > More > Set Custom Ref. This creates a Reference point in time for BBS to track from. Then, when you are ready to check stats, instead of choosing "since charged" you can choose "since custom ref." and it will display all the activity since you set the reference point.
Once you've chosen which stats to view, they are displayed in decreasing order from the most time "awake" to the least. As I mentioned before, most of these are necessary and harmless. Others may be draining your battery. Looking at the screenshot above, you can see that currently the biggest cause of partial wakelocks is "Airdroid". Airdroid is an app that lets you transfer files wireless between PC and phone. I happened to have forgotten I left it on, and as you can see it was running for half an hour. That's not a terrible drain on battery, but I don't want to leave it on anyway. What you are really looking for is processes that use excessive CPU - it will probably appear near the top of the list and may have a red line extending much of the way across the screen. Unfortunately I don't have a screenshot, but previously I found that the Google Backup "feature" was stuck in some kind of sync and kept my processor awake for 11 Hours! Needless to say, I disabled that feature. I haven't seen other people reporting that same problem so it could have just been a fluke, but by using BetterBatteryStats I was able to identify the cause of my poor battery life. Note that if you are streaming a lot of audio you will see certain "audio processes" reporting a lot of partial wakelocks. This is perfectly normal. You may also want to take note of the "count" of different processes as this actually tells you how many times that process caused a partial wakelock. You may notice that things like "syncs" and "Gtalk" cause a lot of partial wakelocks as they are constantly checking for updates/changes. That's why in my previous post I recommended eliminating any syncs you do NEED.
Next up.... WiFi vs 4G