I've knit a few lace shawls and as they are wide, mistakes because I am human happen. If I don't notice my mistake, rather than frogging back rows and rows, I just release the stitches involved. Then I use two DPNs to reknit and correct my error. As I am not straining or stretching the yarn as much to do this, the correction is impossible to see when I am done.
Other uses I've found for DPNs is they make great shawl pins. Either use them plain or use them as part of a shawl pin. Shawl pins don't have to be jewelry, they can be crocheted flowers or leaves made of the same or contrasting yarn. One set of wooden DPNs can make several shawl pins that cost far less than purchasing them. A large wooden bead can be hot glued on one end if desired.
Waste not, want not.
I can do anything with circulars, though I do still use my straights for some projects.
I have just gotten some Knitter's Pride circulars interchangeables which have the same cables used by KnitPicks. So it makes these sets interchangeable. Good thing for KnitPicks kit users as yarn.com also sells the 16" cable. I do not see where KnittingHelp.com sells the replacement parts. Am I missing something?