If it's just something small players can do by watching the trades of bigger players then yeah, it can work forever.
Good question. I'm going to be that guy who answers a question with a question... "How can the strategy of hitting a baseball out of the park and making millions still work if everyone knows about it?" or "How can the strategy of selling a respectable product at a fair price and growing a business to a multi-billion dollar enterprise still work if everyone knows about it?" Sometimes it involves a little bit more.