Read this for battery info: http://www.apple.com/batteries/ipad.html
That mentions 1 charge cycle, which on http://www.apple.com/batteries/ is defined as multiple charges totally 100% (i.e. 10x 90-100%), whereas the link you says it should be completely run down.
Apple suggests doing one complete discharge/recharge cycle a month to calibrate the battery sensor. Beyond that, it doesn't matter. Charge it when ever you need to.
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