My point is after one breeding yes the line is broken, but I still dont claim it to be mine. Your still riding on what the quality of the original breeder/s had. It would be years before I could with a clear conscious.
That's why I say you are "building" a line. It isn't there yet. Until it is...
In 1942 my grandfather started with RIRs and I have part of that flock today. It's been my experience that about every 8-10 years I need to bring in outside bloodlines or something starts to decline--quality, egg laying, temperament--something goes downhill.
As to when a line becomes your own...