There's no way anyone's getting 9 hours on the SP3 unless they have like 1 browser tab open, no other programs open, and they spend multiple hours on the one tab before powering down... I've gone through 5 SP3's, always got between 3 and ~4.5 hours of battery life while browsing with brightness set at 80%.
The battery blows, as it does on most of these hybrid devices (just look at the Yoga 3 Pro, it's even worse). Unless you want to minimize your user experience and squint at 5% screen brightness, do yourself a favor and buy the power cover. It doesn't fit the SP3 perfectly as it was made for the SP1/2 form factor, but it'll bump you up to around 7-8 hours of battery life which is acceptable.
If you want decent battery life the power cover is your only option, either that, or get another hybrid like the Dell Venue Pro 11 with Core M that has a legit keyboard battery and gives you ~ 15 hours worth. Probably the best hybrid on the market so far regarding battery life.
While I don't exactly get 9 hours, I do get 8.5 hours regularly.
Edit: You may not believe this, but then again you seem to be pretty convinced on the capabilities of the SP3 based on your experience (I am guessing). Nevertheless, there are a number of threads here which have discussed this and where people (me included) have posted the relevant sections of their battery reports (which are, admittedly, only rough indicators). You may want to take a look at those threads.