Every time someone purchases an iPhone, it seems like a newer, more powerful version is released just moments afterward. Over the past six years, eight versions of the iPhone have been introduced to the market, leaving so many smartphone users with new-version envy.   The question circling the minds of these not-so-outdated smartphone users then is: Is it worth it to upgrade? Often times, however, the answer is no – especially if the phone is still relatively new. According to NBC...