Same here. The way that I implemented it, I have protection on every page with the exception of
login.php,
newuser.php, and
ubbthreads.php. I didn't set it on those pages because doing so would prevent anyone from logging in, or registering as a new user in the event they had reached the maximum number of page views. As for
ubbthreads.php, I don't mind if people look at the main index for the board and see the forums we have to offer.

It works great. I logged out and browsed around. After 10 page views I was taken to the screen prompting me to either login or register. I have the cookie set to 1 year right now, but I may change that. It doesn't really bother me that people can get around it by clearing their cache of cookies.