Perhaps the BEST B1G Forum anywhere, here at College Football Fan Site, CFB51!!!

Yeah, I'm in the same boat. My work pays for my phone service, but a few years back went to the bring your own device (BYOD) model. At the time that meant that they offered us all a credit towards buying our own phones and I ended up with a Google Pixel 5. Now the Pixel 10 is available and I'm still using the 5.

Battery life is still decent. I keep telling myself that I'd like to upgrade, but then I know it's going to be an out-of-pocket expense. I even tell myself that I might want to upgrade to a folding phone, but then it's a much larger out-of-pocket expense. And I try to avoid doing things on my phone when I can do them on a PC, so I'm probably not needing the upgrade. So as long as my phone [or its battery] isn't dying, I'll probably hold off.

Depending on your plan, potential trade-in value (if any), and other stuff... AND the battery life falling off... It might be time to finally upgrade. Otherwise you might be throwing $200 at a replacement battery but then find a year down the road that other aspects of the phone start having issues and you've basically thrown away that $200.

But I'd ask whether the "battery life is not what it used to be" is that big of a problem? Can you still make it through a day? I know my phone's battery life isn't what it used to be, but I rarely use it enough that my phone drops below 50% in a day and then I charge it overnight. That's enough for me even if it's not what it used to be.

I'm kind of a die hard iPhone guy.  Just had such phenomenal good luck with them and I'm so dialed into iOS I hate to switch.  I have used the Android phones over the years for different things, it just doesn't seem natural the way iPhone does.  Of course, I haven't used one daily, but I can't see myself switching from iPhones. 
Usually what I do is buy the phone out right instead of adding it to my plan.  It used to be about $600-800 to buy a new one.  Not sure what they cost now. 

Yeah once you're into the Apple ecosystem it's hard to disentangle.  It all works so well together, and comparatively poorly with other stuff.  This is of course by design.