I don't know but honestly I tend to lose, destroy or want to upgrade phones within five years anyway. So I'm not that sensitive to how long they last. I don't remember when I bought this one but it's probably 2-3 years old now and so far there haven't been any issues with it.

For me the ability to read on a bigger screen is the selling point. I flip it open to read things all the time. Feels like a small book.