What is the average lifespan of an iPhone 4s?

I spend a great deal of time listening to music, web browsing, and on my social networks. I charge my phone twice a day, and I often unplug it when its still charging and charge it when it is at like 30-40%. I've had the 2 iPhone 4s's for about a year and a half (the first one was replaced at 7 months because of volume button under Applecare, and the iPhone 4s I currently have I've had just over a year and is still working ok. However, I want to switch to Android in December when Applecare expires. Would my phone still be working then? I'm talking about the phone btw, not the battery.

The average life span of a product is 1 year before the battery starts to die out, screen is not as bright, etc.

About 2 yrs on average

Yea, the phone would still be working of course. I had an original iPhone from 2007 up until 2010. Ran fine until then.

Still have my 3gs from '09 as an iPod, 2 4S's from 2011, and a 2012 5. All work fine. Best luck.