Why wouldn't we start S6 search right now?

Of course these parameters depend on the parameters of the source of GW, which is what we are looking for.

We have some idea what objects could emit GW and some models how the resulting GW would look like, but we don't know what and where the sources actually are and which models are right until we found a GW.

We think (or actually just hope) that some of the pulsars we know from radio astronomy are emitting not only radio signals, but GW, too, but most of them are too far away for our current sensitivity.

However the fascinating thing about GW (for me) is that they are something entirely different from the electromagnetic waves (light, radio, x-ray, etc.) that is currently the only source of all information we have about the universe. There may be GW sources that we don't know anything about, because they're not emitting electromagnetic waves, and the further we can "look" into space, the more likely it becomes that some GW sources are within reach of our instruments. So we are simply pushing the sensitivity and thus the reach both of our detectors and search algorithms further and further.

BM