I bought an iPhone 4 on July this year, and the warranty is valid until July 2012. About two months later, there were rattling sounds from it.

I went to Maxis and got it replaced with a refurbished unit in a visit. All good except the warranty of the refurbished unit is valid until Jan 2012, which is clearly shorter than the initial unit.

I know this only after I check with Apple's Check Your Service and Support Coverage page, here http://goo.gl/ZG7LN

Oh is it? Maxis told you this? Where it is mentioned?