When fully charged, it does seem to hang around 100% for a while which I think gives a false sense of longevity. When it starts to drop a few percent, it may appear that battery usage is speeding up. As has been stated in previous replies - 10 hours use equates to 1% every 6 minutes but of course reviews have found battery life can last well over 10 hours under favourable circumstances and much less under stress. I think your figures seem fairly accurate. If you are on Safari, you are presumably on Wifi too which uses up battery. What is your screen brightness at? Are you only uses Safari or anything else? Is bluetooth on even if not connected to anything?