It's a personal preference. I have a friend who almost always uses it because nothing it turns off or throttles is important to her and she's more interested in battery saving. I use it when I expect not to have access to charging for a while and know I'll need the phone.
When Low Power Mode is on, your iPhone or iPad will last longer before you need to charge it, but some features might take longer to update or complete. Also, some tasks might not work until you turn off Low Power Mode.
Low Power Mode reduces or affects these features:
- 5G (except for video streaming) on iPhone 12 models1
- Auto-Lock (defaults to 30 seconds)
- Display brightness
- Display refresh rate (limited up to 60 Hz) on iPhone and iPad models with ProMotion display2
- Some visual effects
- iCloud Photos (temporarily paused)
- Automatic downloads
- Email fetch
- Background app refresh
From: Use Low Power Mode to save battery life on your iPhone or iPad - Apple Support