Thats terrible advice, just because there is a 5 or 10 on board doesnt mean you need to watch for straights. What if the flop is ace 2 4 6 7? no five, doesnt mean you dont have to watch for the straight. And also, if theres only one or two possible hands that make straights you shouldnt be too worried. You can also watch for betting patterns showing that they are chasing or have the straight.