This in itself is a really interesting topic to me. I never let my phone get down to zero charge but is charging up to 100% really discouraged? It's the first I've heard of the 20% and 80% thresholds for charging. I feel like my phone is doing really well for being 4 years old now. Oh and I am familiar with the Nova launcher. My previous phone was a Note 3 and I downloaded the Nova launcher at the recommendation of a friend. Anyway, all good info. Thanks!
It's not discouraged, as the handset makers want you to buy a new phone every 2 years
they want you to have a run down battery or a cracked screen, the 2 most common factors for changing phone in the real world. You having a 4 year old phone is brilliant and shows you take care of your handset more than the average person, but handset makers are losing money on you. So if you're happy with your battery health now, you're doing the right things in general anyway
Charging to 100% is fine typically, as long as you disconnect from the charger ASAP, its just easier to track taking it off charge around the 80% mark or have your phone specifically stop charging at that time. Gives you a buffer zone of sorts. But the battery "memory" takes into account that you've hit 100% and waits for the next 0% for it to count as a cycle, or that your phone is at 100% for a while for whatever reason. Just like laptop batteries, they learn (not as) quickly that they like to be connected constantly to a power supply. The 20/80% numbers keep your phone charged and battery in good health
That being said, at least to begin with, you wouldn't notice any negative battery health in the first year if all you did was 100% to 0%, you'd be able to claim on insurance or warranty (standard is 1yr and only covers very specific things usualy, hence insurance options or extended warranties) for faulty battery, it would start to show in 2nd year onwards, they are sneaky like that. By 2nd year its very very easy for handset maker, insurance provider or shop where you originally bought from to just say "its fair usage after this amount of time" and its then upto you if you want to prove that the battery is dud by going through hoops
Battery will typically charge quicker (it's capacity has shrunk so reaches 100% faster) and be used much quicker than it used to once at 100%
There's all sorts of little hidden away settings to turn off (or on) to help improve battery life, but they obviously depend on if you really use them or not. There's 2 specifically I turn off right away, wifi scanning and Bluetooth scanning (sometimes called device scanning). And disabling or uninstalling as much bloatware as possible helps. And closing down apps in the background! Especially ones constantly updating like Facebook, weather or news apps
Anyway, I'm creating a wall of text here that is reeeealy boring to most people lol as much as I'd go on and on about it
My honest opinion, take on everyone's feedback, but remember everyone is different and uses their handsets for different things. Your 1 best bet is looking at your past history with handsets and how it holds up 2/3/4 years down the line. If you find yourself wanting/needing a new phone after 18 months to 2 years, it's either a fashion accessory, you have lots of disposable income, or you've mistreated the phone. If you can make a phone last 4 years, any phone you get with the same care and usage will be fine in your hands
Tldr; batteries are made poorly on purpose but you can look after them by turning off things and unistalling rubbish and not leaving them on charge