Last month the battery life on the PinePhone was just as bad as on the Librem 5, but they have improved some things in Crust (the power management firmware) and repowerd. It is now possible for the cellular modem to receive a call and wake up the phone to notify the user.
UBports developer mariogrp reports that after 10 hours with the phone in sleep, he still had a 34% charge on the PinePhone battery, so you should be able to get 13 hours with the PinePhone in idle and getting notifications for phone calls. Of course, if you are constantly turning on the screen and using the phone (web browsing, texting, etc.), the battery life will be much less, so you probably will still have to carry around a second battery to get through an entire day, but the PinePhone is getting closer to being a usable phone if you use UBports. It will take longer for these changes to make it to the other ports.