I say leave them alone too and work with your plans. Right now I have 6 large tops hand pieced like that, appears they'
re from the 30s/40s/50s and I've machine laundered using the heavy duty setting and so far they haven't raveled on me (or come apart). I guess they used good quality thread in those days. Apart from the tops, I have a good sized collection of blocks pieced that way which I've laundered and they're still intact