Mine aren`t too bad, but I try to look after them, bend the page rather than the spine, that sort of thing. It always makes me wince when I see someone open a book, put it on the table and just run a hand down the middle to flatten it out.
Those are the people that you wish would read by osmosis....
None of my Normandy books show any weakness. I'd be suprised to see an "Open Fire" rulebook that wasn't out of its binding.
I bought Fortress Europe on sale, I suspect, for the loose pages it had already. Out of habit I spiral-bound my "Das Book".