Until you start seeing those weird numbers.. Your phone turning off at 15% which I have happen three or four times a year. Or doing a full charge and it only registering to 99%. These are all symptoms that it's time for recalibration. I agree that in terms of every day activity or even every month activity this isn't something anybody has to worry about.
Right out of the box, a new phone, needs to go through one full recharge cycles to give you the best battery stats and most accurate. That's why this issue came up in this particular thread where people are comparing their battery usage to older phones. Out-of-the-box your phone needs one of these "full charging cycles" before it will read completely accurately.