I was in the SAME BOAT! 13 Pro Max, still in near mint condition. Only issue was the battery, that's it. I went t check out the new phones yesterday...and it was a mixed feeling. Flip flopping between keeping 13PM and upgrading. Honestly the new phones looked and felt better in person...better than I expected. I actually thought the Silver was nicer than Deep Blue...didn't expect that. And yes, a lot more new features compared to this 4 year old phone. Is the camera(s) lenses, photo quality better? Yes, it is. Although a few pics I took in 8X, I wasn;t impressed!! Depends on lighting I guess. And well, yeah we still have the slow lightning port. USB-C is better..but for now I'm fine.
I simply asked the one Apple employee about getting a new battery, whats the process. Stated it's $89. Ok...I don't know why years ago another Apple employee stated "we run a test, the battery replacement is '$239!" SO...I just thought "to heck with that!!"
For a while I thought getting one myself and TRYING to do this on my own..I did it before, but before Face ID on XS Max, 6 Plus..etc. Or 3rd party repair shops....but I did this before on iPhone 5 and the guy put in a junk no name battery that ballooned up in a month.
Anyway..I walked into Apple this morning, wanted a new 13 Pro Max battery. They did run the test, what shows as "89% Health" on my 13PM was actually "82.3%" that's quite a difference and explains the horrible drain in the last 9+ months. I really haven't trusted that iPhone "Battery Health" % for a while TBH. So 45 min. later, it's done. "100% Health" - Yet Coconut Battery shows "102.4% - 0 cycles." I'm happy. No problems keeping this for another year at least....hell maybe until Apple stops supporting it.
The 13 Pro Max still has the 12MP RAW photos...for me that's fine. I can edit these in Lightroom/ Photoshop, if you do a lot of photography. 4K video, there are 3rd party apps like BlackMagic, FinalCut Camera, and others that takes great video...these can use older Apple Log uncompressed video format (those are MASSIVE files though, I barely use that)
As for iOS 26 and causing drain...ugh, I do expect it to some degree now, but...I HOPE I won't lose 10-15% battery life in 20-25 min. of simple normal use. I just may turn off the Liquid effects, animation ('Reduce Transparency' in settings, that might help a lot)
Not that it matters, I did explain to the Apple Genius employee this morning about I was quoted "239" years ago, he had NO idea why I was told that. Did state "older phones...7, 8+ years old can be more expensive, but not 200+ dollars"