I've used my (original) SE for over 5 years, running it down to the 20% region (often way lower) and back up overnight at least 2000 times. Battery still seems reasonable - health on 79%.
May I ask where in the world you live? I wonder if part of the cause of your incredible battery longevity is a climate that stays safely within Apple's design specs of low humidity, moderate temperature. I've lived in areas that get very hot, very cold, and very humid regularly in the time I've owned my SE, which could contribute to battery degradation.
And above it all, batteries are very much a lottery. Sometimes you get a really great one, sometimes your battery falls apart within a year. I guess you got lucky.
Before I had an 11 I had an SE, and by year 2 or 3 the battery was so weak that I had to carry around an external charging pack for it. This got really awkward (and a little scary) for traveling and was part of the reason I upgraded to a newer model.
Right before I sold that SE to my friend I checked the battery health, and it was in the high 80s. Yet I could not get a full day's use on a single charge. This led me to conclude that that Battery Health measurement was bullshit.
Apparently if I enable analytics I will get a report saying how many cycles my batter has lasted. Unless I use my phone for several hours of playing spotify and youtube I don't notice the battery dying during the day.
