Devices like the iPhone and iPad are not anything like a running PC or Mac. The components are completely different and the way the devices work cannot be compared. Therefore, you can’t just apply the same rules for shutting down a computer to an iPhone or iPad.
For iPhones and iPads, the only real reason you would ever need to shut it down completely is if the device is not working properly and if you want better battery life. If your apps are freezing or not opening properly, etc, then it’s probably a good idea to do a full shutdown and reboot. An Apple Genius employee told me that turning off the iPhone or iPad at night will help extend the life of the battery. Why? Because most people keep their phones connected to the charger all night and that doesn’t help the battery.
Otherwise, you can pretty much leave them on the whole time. The iPhone and iPad have short sleep times and therefore don’t stay on for terribly long anyway. The sleep setting will also lower the power usage of the device.
The only other time I could think of that you would want to shutdown is if you wanted to really conserve batter power. Maybe you got stuck somewhere and you only have 15% battery life left. Even on the sleep setting, the battery will be used. So you can turn off the device to converse battery power.
For iPhones and iPads, if you just want to conserve battery, you can also put the device into Airplane mode, which turns off the WiFi radio and 3G/4G. In terms of extending the life of the flash storage, it’s probably better to keep the iPhone or iPad on as long as you can. Since it’s using flash storage, the more writes to the drive, the shorter the life. Turning your device on and off probably performs extra reads and writes to the storage, so just leave it on unless the OS starts acting funny.
The optimal configuration is probably to turn if off once at night unless you need it for important calls/emails (to extend the battery life) and that’s it. It will take a lot of on/off to really reduce the life of the storage, but the battery will definitely lose it’s luster faster so shutting down could help. Again, though, since people tend to use their phones at night also for messages, email, etc, turning off is not a big deal if it’s inconvenient.
As you can see, there were a lot of If this, then do that, else… in this post. For each specific person, shutting down depends on what you value more. As a general rule, if you do want to shut down, do no more than once a day.
And doing so once a day will not damage your PC, Mac or any other device.If you’re not using your device or computer for anything at night, it is better to shut down. It will extend the life of a PC/Mac and let your iPhone or iPad battery last longer. This is a hot debate topic, so what are your thoughts on shutting down every night?
"iPhone or iPad Tips: When to Shutdown an iPhone or iPad"
Reference : online-tech-tips.com