yes, assuming you producing audio , and the function is in the audio thread.
1/3000s - patchtime.
(where patchtime is the time take by the rest of your patch to execute)
if you don't complete in this time, you will get audio glitches, because the output audio buffer will not have been fully processed.
(bare in mind: k-rate code is executed in audio thread, and the entire patch is 'rendered' before the output buffer is copied to the codec)
if your not producing audio output it doesn't matter...
if your function is taking a long time (or indeterminate time) then it should be executed in a separate thread.