How long will an iPhone actually last?

Ok so I have this iPhone 4 in excellent condition that I've had since 2011. I haven't dropped it or anything but I still use it. How much long will it "actually" last before the led light goes out or it becomes unable to use to to wear?How long will an iPhone actually last

I have the iPhone 3GS and it's on it's third year, still works well without any problems and performs like a dream.