If you clip as you make your blocks and as you construct the top there is less ) clean up) to do before quilting. Being a longarm quilter I can tell you it is definitely appreciated when the customer delivers a nicely done quilt top. When I have to spend an hour ( or more) cleaning up loose threads it is aggravating and sometimes I have to charge extra for the service. If you only clip the ones you think might show up and leave the rest there will be ones showing through! Mainly because as the quilt ( sandwich) is advanced on the bars those ( left behind) threads move and wind up where you do not want them and it is a pain to try to remove them in the finished/quilted quilt. The backing/batting behind them really enhance them showing up in the top.