They may or may not wash out. There are so many things on the market. I got some stuff (can't remember the name) that you leave soaking in the sun that is supposed to remove yellow from antique quilts. Who cares, yes you should finish the quilts. It's a record of how far you've came. Who knows, if you'd completed it 50yrs ago and it had been well loved for all of those yrs there could have been "stains" on it by now anyways. Finish your accomplishment.