Sure, all the backstories about Robert's Rebellion and such are much of a mystery to the TV viewer, GRRM may want it that way so they buy/read the book. But Im beginning to think they will make note of the details about some of the POV characters in other scenes.
Look at Tyrion's first battle. In the book he took the left flank and protected the river; that whole fight from the moment Tyrion woke up till his father telling him they won took 2.5 mins of screentime. That was a whole chapter in GoTs.
Look at Catelyn's trip to the Vale. Sure they follow the book pretty well up to the Bloody Gate, they sure as hell didnt waste 15 pages describing the trip from the gate to the base of the castle, then describing the bastrd girl who tends the mules then describe the ascent for Catelyn and the basket-ride for Tyrion, then the Catelyn having to wait until Lysa will receive them. blahblahblah.
Pages:
GoTs: 694
CoK: 708
SoS: 973 (Two seasons, presumably everything up to the Red Wedding, then everything after)
FfCs: 753
DwD: 1040
The content for FfCs and DwD will all happen in realtime for the show, none of this geography splitting nonsense. I assume that will still be 2 seasons worth because it is just telling what happens from new POVs, but would anyone really care if they take 3 seasons for those 2 books? 10 more hours of content and added POVs would be amazing.
So the end of the 5 books will either be 6 or 7 seasons. 60 or 70 hours should be plenty of time to tell this story. You need to remember this is equivalent of 30-35 two-hr movies. If there are some details you think they miss, you are nitpicking.