In my experience, batteries start to deteriorate after about two years or so.

Planned obsolescence wiki link

For me it's just an unhealthy fascination. Tech is the one place where consumerism got it's dirty claws in me. We didn't have a computer in my household until I was 15 and it was a super slow and old PC my older brother bought for $500. This was back in 1999. I eventually became obsessed with finding the best value for money mobile devices and bought way too many phones, laptops and computers.

The Google Pixel 7P that I have now I bought because I dropped the 6P on the ground so bad that it wouldn’t even start. The 6P I got because it had significantly better camera and was faster than the OnePlus 6T I had before. I know you say 100mp doesn’t make a difference from 12mp but there’s really a huge difference in image quality with the Pixel compared to the 6T, especially in low-light conditions or when you zoom. And it’s not just me, people have been commenting at how good the pictures are without even knowing what phone I own.

I also enjoy new features like the gestures to control apps. Overall, apps and the OS get slower because new features keep being added, and security updates stop coming, so I need to renew the hardware to keep up. I use the phone for hours a day every day, all year around, so I think it’s worth putting some money into it. But I don’t get a new one every year. Maybe 3 years, or possibly 2 years depending on what gets released.

For me, I kept my last phone for 3 years and upgraded because I didn't have enough storage. New phone is a little nicer, has a few new features, but I may well keep it for a few years again.

I have a Pixel 2 I picked up in 2018, a few months after they were released (my previous Nexus 5x got the bootloops).

I held off upgrading due to the free original quality Google photos. When that ran out, I did follow new releases, and found the features appealing, but then I'd see the ever inflating prices and couldn't justify spending so much to replace a device that still works fine.

And it does still work. Granted, it's had a new battery and a couple of charging ports (I've gotten a lot bolder with cleaning the ports now, don't expect it to need a 4th any time soon). I'm fortunate to be capable of making those repairs myself, I'd have probably given in and bought an A model otherwise. For now though, I just have to say, maybe next year.

I finally had to upgrade after 5.5 years because software support was lagging for the version of Android I was on.

I buy a new phone anytime a new innovation comes out. I ordered the Google pixel on day 1 and am loving it.

I just enjoy new tech and trying new things in that arena. So new phones before I technically need to is one of the things I spend disposable income on when something in that arena catches my interest.

Does have a nice side effect of constantly reenforcing the use of platform agnostic services and retaining ultimate control of my data if it is something I care about, since it really allows me to just move the sim to a new phone and be up and running in a hour or less with more or less any Apple or Android phone.

There is a HUGE difference in 4 and 12 GB of ram if you're using 20 different apps at once that are all running background tasks.

The camera raw megapixel are of little significance these days but things like optical zoom or a larger sensor and aperture make a lot of difference.

The main reason to upgrade otherwise is unsupported OS versions. you'll stop getting security updates leaving your phone vulnerable to attack.

I usually break my phone within 12-18 months because they're so damn cheaply made. Why so much glass?

If I could go back to a Treo600 I would do it in a hot second, that was a great phone. I had it for years, it was mostly plastic that I beat up quite a bit, but they use gsm bands that aren't supported anymore.