That's a tough question to answer; given the nature of the coherent beams of lasers it should be sensitive at "any" distance. I quickly got a signal at ~12 meters distance (the longest clear span in my house) without tweaking the laser focus, frequency, or power and didn't take it any farther. My goal was only to build a laser tripwire and I wasn't attempting long distance communication.
Did you use a modular IR receiver like is used in typical home IR remote controlled electronics? If so, which particular one did you use?