On my DMS I change at least every project, thread type change or when I hear that "thunking". On the long arm it is at least every quilt, although I'll use the same needle if I'm doing back to back crib quilts, etc. I figure changing the needle is somewhat like changing the oil on my car--a good preventative. Question--where do you buy Organ needles? I can't find them locally or JAF, Hancock's etc and sure do prefer them. Otherwise use Schmetz.