it depends on what is your battery condition, if your battery can only last like 2-3 hours from fully charge normal usage, then your 1% isnt much compare to a brand new which can fully charged can last 10 hours. if you overcharge it too much or use it to 0% too often, your battery life is dramatically reduced, from what i read, they suggest do not charge over 100%, or use it till 0%, when charging, better stop when the charging is more than 95% and overnight charging is very bad.

it also depends what kind of application is STILL running when your ipad is sleeping, same to some smart phones, even they are sleeping, its still running some app, and i think ipad should be able to last much longer in sleep due to it need not to connect to telco(3g is different story), and even its much larger than phone, it dont consume more than a smart phone if its in sleep mode.