If you're like me and you swap phones the second a new one comes out, then don't worry about it and just try to take as good care of it as you can. You've got an incredible 1 year warranty from Apple and GREAT customer service. The only thing major that AppleCare+ provides (someone please correct me if I'm wrong) is the extra year of the warranty and two swaps for any breakage/accidental damage, no matter what, for $49 each. I got mine on eBay too and tried to do it, but they said no dice because it was over 30 days after the original purchase. They didn't say anything about an original receipt because they can check when it was purchased.
You have a year from purchase date to get regular AppleCare for $69 which I believe is just an extension of their warranty for an additional year.
Next iPhone I get I will make sure to get AppleCare+ when I buy it. Just in case. It's definitely worth it for the accidental damage coverage.