Can we use some common sense?
If you're already established in cruise and everything is working fine.... don't touch it!
The unreliable airspeed procedure calls for less power than cruise but more pitch. That sounds about right for stabilizing at a lower airspeed. Basically, the procedure is designed to apply under most circumstances—i.e., if you're on approach, on climb out, maneuvering in the terminal environment, etc.
This is a VERY generic procedure. Why are you trying to get specifics about when and where and how you should apply this? Just do it! The airspeed can be "unreliable" for many reasons. If you think it's unreliable, then follow the procedure. It's simple. Boeing has already done the work for you, Mr. Captain, just put the airplane at 4 degrees pitch and 70% N1 and that will stabilize the airplane so that you can use your exceptional thinking and experience to determine what you'll do next.
