Is it safe to leave my iphone plugged in and on safe?

I have to download sometbing that will take multiple hours, i eould like to know if it is safe to leave my iphone 4s plugged in charging while the screen remians on. Will the screen stop working?

The phone will be fine. One you start downloading, just hit the lock screen button at the top-the phone will continue to download. As long as you do not power off the phone, the apps, downloading and other activities will still stay active.

Its safe, I have an iPhone 4S and keep overnight downloads on overnight with screen on (low brightness) and works great! Every few days a week!
Jutst to be on a safe side, I try to bring the battery % near 15-20% and let it do its thing!
But make sure to keep the phone somewhere far from U! As electronics can never guarantee any type of safety!