At this point, I'm finding that sleep works and it only drains 0-1% over night and I haven't had any high activity during sleep. In terms of battery life during light use, I'm still getting about 6-7 hours with what I have installed which is good enough for me. I think, just as an experiment, I'm going to try disabling some background tasks, namely OneDrive and Cubby syncing as well as Bluetooth, to see if I can push it even higher.
First test after disabling my cloud storage synchronizers and Bluetooth, things look promising. I used my SP4 for an hour over dinner and then 43 minutes late at night when I couldn't sleep, both times to mostly read Reddit, MarketWatch, and NeoGAF on Chrome with AdBlock running. During the first 1h02m, it went through 12% battery and then it went through 1% during 5 hours of sleep followed by 9% battery over 43 min. Turning it on today, it went through another 1% during 8.5 hours of sleep. Given 21% battery over 105 minutes of usage, that gives a projected total battery life of 500 minutes or 8.3 hours. Prior to this, I was averaging about 6.5 hours total with similar usage scenarios, thus my early conclusion is that OneDrive and other cloud syncing services are a huge battery drain. I had an inkling that this would be the case since I would often see the OneDrive process spike the CPU usage up fairly often, presumably to scan for changes both locally and online.
So, if you're really concerned about battery life, turn off your automatic cloud synchronization services, things like OneDrive, Dropbox, Cubby, and Google Drive.
I think the best way to task battery consumption is to use an application such as BatteryMon. Then it is a matter of logging power consumption and match it to different uses during the day. CPU usage can be used as indicator, but most of the time, battery drainage is due to hard drive or screen activity.
One of these days, I wish manufacturers will quote battery life in "average" use. SP4 doesn't really do 9 hours. They should say 6 hours of web browsing. Then when people get the unit and do other things that would use LESS battery, reviews would say, "Look! I got 8 hours of use!" That would sound better than, "Look! I got 3 hours less of use!".
I hate being at 100%, browse for about 10mins and be at 94% (Yes, it's probably due to all those animated ads). I know I shouldn't watch the battery icon, but I MUST click it when I see it.
I haven't posted here in awhile since I haven't really done any solid battery use until today. Today, I was at a conference where I was taking notes in OneNote as well as using Chrome to look up webpages and viewing the programme pdf with Xodo Docs. My SP4 was screen on for 307 minutes (5.1 hours), on overall for 10 hours including sleep, which drained 69% of the battery. This would lead to a projected battery life of 7.4 hours. This is only one data point but might indicate that the recent updates might have improved battery life a little bit.