I've had the SE since May 2020 and it's still fine. Settings reports 98% battery health.
As mentioned, I'm a very light phone user. My average daily iPhone screen on time is 30 minutes or less. I mostly just use it for quick lookups, messaging, short 1-minute calls (e.g. Where are you?) and the occasional pic. I can actually get away with charging the SE just every other day.
My iPhone 7 lasted 2 years with decent battery life with similar usage (typically 20-40% remaining at end of my 9-hour shift). With the SE, I typically have 50+% remaining so I expect the SE will be able to last just as long or longer.
Mind, ever since I got a wireless charger for the office, it's gotten a lot more convenient to charge my phone during the day. Instead of charging overnight, I've just been using the wireless charger to charge intermittently throughout the day.
AppleCare+ extends warranty as well as covers accidental damage (up to 2 every 12 month period, iirc). It also covers battery replacement. I pay $3.49 per month for AC+.