upgraded from the 7 to 13 pro max in december. even after a battery replacement in jan 2021, with 90% battery health and ios 14, it would die super fast with my usual use, which is relatively heavy. less than 2 hrs battery life if i was playing pokemon go, or browsing the internet, or watching youtube. if i opened a pro camera app like moment it would die within 30 mins from full. it also did especially bad in the cold, during some winter days the average use was less than 1 hr, the cold just kills the battery so quick.
if you use your phone more than 10mins/hr a portable battery/charger is a must. obv a used 7 is pretty cheap now but you can find 8's for not a lot more. i don't have personal experience with that but my friend used to use hers more than me and it lasted many hours, don't have a number but enough to not require carrying a battery/charger everywhere.