My friend with a 12 mini complains it's still too large and basically always needs to have a purse with her since it won't fit any of her pockets. Never complained about battery life and doesn't cart any external power source, either.

Different friend had one of those cases with integrated battery packs around her iphone pros. She spends her days on the phone, though...

As another data point, my iphone 7 had basically enough battery to last me through the day until last year. I changed it because the battery was bulging, and at the end the screen was hanging on to the body by next to nothing.