I don't know about anyone else, but unless I'm eating 6 double whopper's per day, it takes some planning to eat 300+ g protein. So I wouldn't even be worried about taking too much in. Just take in 1-1.5g/lb protein.

I personally have taken in as much as 400g protein before and felt fine. I drink plenty of water and my piss is always clear, so obviously my kidney's are working fine. I currently take in about 300g protein, and that's on paper. I gotta plan meals out to hit that high. I wouldn't worry about takin in too much protein. As I said, 1-1.5g/lb protein is fine.