Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Perhaps do some tests yourself over a period of one month, charge, use, how long it takes to fully discharge, how long it takes to charge. Just do regular use and write your data in a spreadsheet. then take a decision at the end of the month if you think is necessary to take it to the store and claim a warranty.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.