I have the habit of always using my smartphone for at least 3 years as long as it's still in good working condition before having to replace it. Most of my smartphone lasts 3 years in my care except for the one that was stolen and the one that fell into water.
My current Samsung Galaxy S20FE is just barely one year in my care. So, we have 3 more years to go.
I change my mobile device almost every 14 months. There is a portion of my monthly earnings that I save which I use to buy a new device yearly. This has helped me to keep using one of the top Samsung devices that are in the market.
I make sure that I charge my phone every night before bed because I use it a lot during the day for personal and work related reasons and it drains the battery quite quickly. The worse thing that can happen is if it loses it's charge during the day because then I feel like I'm missing something and can't get my work done. So for me, I stick to a schedule of every night I charge my phone to ensure it's at 100% in the morning.
My current phone is two and a half years old. I used my last phone for 3 years. I use a phone until I can use it, I discard it when the phone is beyond repair. I use budget phones.
I have an iPhone 12 that I got about 3 months ago so it has a very good battery. I try and charge it only when it's quite low but I don't charge it up to maximum capacity though as I heard from a friend that was bad to do so I make sure I don't do that. I charge it maybe once every couple days. I don't use it too much.
When it comes to changing my phone I usually do it every two years unless I have issues with it and feel like I need a new one sooner. The phone I have right now is the Huawei P30 Pro and I have had it since Christmas 2021 when my daughter upgraded to an iPhone. I still have the same phone now and it still works after my having it for just over a year and my daughter using it for a year prior to that.
I have a feeling I will be upgrading my phone though within the next year if not sooner but for now whilst it still updates to the latest version of Android and whilst my phone still works with the apps I use I will keep it.