so was the point of this to give you more battery life? i am wondering! i am always trying to upgrade to latest and was so happy to finally get to oreo with my galaxy s7's (tho one did not update ota not sure why) SO what was your OST (On screen time im guessing?) before the update?
OST=On Screen Time was 5 to 6 hours but after this years update (Final Update for Galaxy s6) the battery drained faster as it lasted only 3 hours OST.
Basically I don't flash any Custom Roms what I do is Revert the Security Patch update back to an older point if I am having trouble with the latest update, like in my case. So for example Android 7.0 Nougat has several Updates. One can be March 2017, then June 2017, and so on the entire year. What happened was that the last couple of updates drained the battery on the Galaxy s6 tremendously, many say its on purpose so you would discard this old phone and buy a new one, but who really knows.
So I looked online and found the November 2017 update to Replace the April or May 2018 update that was causing the battery drain, hence the need to FLASH it manually using your Computer and Odin. Since Samsung phones do not give you the option to rollback to a previous version of an update through the phone nor can they be uninstalled once installed.
If you are not having any problems with your phone this is probably not necessary specially being that you already received the Oreo Update on your Galaxy s7. In my case the s6 isn't going to get Oreo but there are ways you can Flash it to get Oreo or any older Version on it. I just want 7.0 since its the most stable and better looking for my phone.
Sorry for making it over complicated hehe.