This is definitely an issue and one I'm quite surprised MS did not address. Well I'm just assuming they didn't address it because the stated battery life of the SP4 is 9 hours, same as the SP3. Hopefully the SP4 will run closer to its specs, unlike the SP3. Without baying, full brightness, and mainly web browsing, email type stuff I can get a solid 6 hours out of my SP3, sometimes more, but I've never gotten close to 9 hours with typical use. It shouldn't discharge so much overnight, that's not normal, but windows hibernate has always had issues since the beginning.
The iPad are phenomenal in this sense, they last for a long time. But it's a trade off in how you use your tablet. If you simply need a consumption device then definitely stick with the iPad, although personally I'd MUCH rather consume content on my SP3.
Also keep in mind the comparison, the SP3 is not mean to be compared to the iPad. Although in all fairness the MacBook air also gets more battery life than the SP3. I'm not sure that the surface 3 real world battery life is, but that's a better comparison.
I of course realize that the iPad is not directly comparable to the Surface line, the problem is that the Surface is supposed to be a device that integrates both work and casual computing into one. It's a great work device. But it's still a poor casual, personal device, so it fails at one of its primary goals. I can't rely on my Surface to have the battery life I want (or even for it to have any battery left when I want to use it) so as I result I still end up carrying my iPad with me. I'm basically fine with the size and weight of the device as a tablet - and enjoy the larger screen - but for casual use reliable battery is paramount to me, and I have yet to see a Windows device ever deliver on this front.