We are already talking about this topic in this thread:
Cutting cost: Do we really need the latest smartphone? so I will quote in brief what I said there:
-snip- I recently heard that every time you change your smartphone before the end of it's life cycle, your hands are a little more stained by the blood of many slaves who work not only in the coltan mines but in many other points of the production chain.
Better for your pocket, better for the people, better for the planet. Getting the newest device for the sake of fasion is just another madness of our times I try to avoid.
Looking at some
statistics I found, it seems that 14% of people change their phone every year, and 6.6% do it every six months (that's crazy). The average time to upgrade the phone, on the other hand, is between 2 and 3 years.