Some information about the whole battery life thing.
For starters: It’s never under ANY circumstances called “battery backup”. NO. It’s not. Regardless what they tell you. “battery backup” or “backup battery” is a secondary help battery to a system (like a computer). Correct term is, and will be, battery life.
Using a phone will use battery
Yes. As simple as that. If you use it more, it will use more. Use it as a toy and it will of course be have a “bad” battery life.
Where you use your phone matter
This assume you’re using it on mobile data. When moving around it will cause the phone to search for better cell towers, and it might up the power of the radio as well. And, if you’re between two cell towers it might switch between those two. Which will cause it to use more battery. 4G LTE can be very power hungry at times. So, is there’s a wifi around that is what you should use.
And, if it’s warm (above 35°C) around battery life WILL suffer from this since the type of batteries used today gets less efficient when it is warm/hot. Some makers uses 35°C as the upper limit for when a phone should be used. Just avoid using your phone out in the sun on a hot day. Or even inside if it’s hot there.
What you install matters
A LOT even. If you install every app and game you see in play store. This might/will lead to more battery being used. And, it comes down to just WHICH apps you install as well. Don’t assume it’s good just because it’s in Play store. And, oh: avoid installing apps from outside play store. Unless you REALLY knows where it comes from. And you really know what you’re doing.
No, updates doesn’t make it worse
This I’ve seen too many times. No. Sure, some android versions are a little “odd” but as a rule: Nope.
BUT! this assumes that your phone is nice and clean. Having too much crap installed, and it will suffer. Of course. I would recommend that you look into doing a factory reset around update time.