Here are two common approaches to instrumentation. One way is to place numerous calls to FFSTProbe throughout your product to get broad coverage. This approach might contain only a minimum amount of error data since you know every error would be captured via a probe. The second approach is to use just a few strategically placed calls that capture greater amounts of error data to better isolate the the exact cause of the failure.
The advantage to the broad coverage approach is that errors are most likely to be identified because of the greater number of calls to FFSTProbe. The strategic approach usually involves instrumenting existing exception paths or thoroughly understanding the code to identify where to place the call to FFSTProbe.
You might consider combining both approaches in your code. The broad coverage aspect identifies exactly where the error occurred, and the strategic aspect identifies the cause.
You should use FFSTProbe only to detect problems that would require a program fix or a modification to user operation procedures.