This is another reason experts advise against charging your phone at night. You may have noticed that its temperature may have increased while charging your phone. This can become a fire hazard if the phone gets too hot and you’re sleeping, unaware of the impending dangers. In an interview with The Guardian, Paul Shaw, of Staffordshire fire rescue, discloses that charging your phone under a pillow or on bedding is called, “thermal runaway in the battery. It self-heats. It keeps going and going. A work surface or wooden side table are fine, because the battery won’t output enough heat.”

The Bottom Line
There are ways to help prolong the life of your battery. While charging at certain times of the day doesn’t matter it’s a good idea not to charge your phone for long periods of time after it’s fully charged. There are also features you can access on your phone to optimize battery use. In iPhones with iOS13 and beyond, you can enable Optimized Battery Charging. Once enabled, your iPhone examines your charging habits and waits to finish charging past 80%.

Optimize in Other Ways
The overall life span of your batter is great of importance, but so is how long it lasts you between charges. Nobody likes it when their phone dies at the most inopportune times. Samsung shared some ways to prolong your everyday battery life:

Downloadable apps that monitor background programs to close them when they’re not in use.
Turn down screen brightness or disable auto-brightness mode.
Avoid using live backgrounds.
Set the screen to timeout at a faster rate.
Disconnect from Wi-Fi and Bluetooth when they’re not being used.
Remove Widgets.

References

True or false: You shouldn’t charge your phone overnight.” USA Today. Kim Komando. March 14, 2021.
“Why You Shouldn’t Charge Your Phone Overnight.” IFLS. May 2023.
“11 tips to extend your Samsung Galaxy battery life.” Samsung.