As a 12 mini user daily since it came out in 2020, I've only just now started to hit any noticeable battery dip (~85% after almost 5 years usage). It's still pretty solid on a daily basis. On very rare occasions, the smaller battery has required charging before evening due to excessive photos taken and/or nav without a plug.
FWIW, I will probably replace the battery by end of year, or next, and keep it going as long as I can... I refuse the massive "normal" phone size.
Imma big Mini fan but the battery is sorely disappointing after a year on both my 12 and 13. It's especially true in daylight when the display goes max; walking the dog for 15 minutes sees a 10+ % battery drop. It's nuts.
That said I wish they'd release a thicker version to compensate
