I have a 13 mini for about 3 years now - still holding up for most of the working day (about 15 hours). The trick is to reduce the number of apps you have on the phone, reduce the number of apps which like running on the background, and not watch a lot of videos.

I figured it out that treating it as a communication device + payments device + maps + very occasional content viewer, ie mostly as a utility will make the phone last much longer.