I couldn't stand it any longer. I had done a piece of needlepoint involving a gray cat and had put black whiskers on him, which seemed to dominate the whole scene and made him look more like a rat. It was the suggested color, but....
Took it to my framer, she took it all apart. Once home, I spent probably an hour with tiny scissors and tweezers pulling out those black 30 or so stitches. The canvas is very fine - prob. about 16 mono. At any rate, I redid the whiskers in a paler gray and it looks so much better. I was also amazed at the number of holidays I found elsewhere, so natch, I fixed those too. Glad I had kept the scrap in my stash. I managed to sew up the back and get it back into the frame with no trouble.
If you really aren't happy with something on your wall, re-do it. I'm just sorry I waited so long, like about five years.