An entire project? Not SO many times.
But parts of it/ beginnings... well 4 or 5 times, I guess.
My horror in ripping was this really nice ribbon style yarn, white, relatively thick that I had this spring. I had bought 2 balls, and could not get any more at that point (NOW they carry it again, duh!)
But I wanted to make something for a newborn out of it. Well, not so great. I tried like 6 different things. Everything turned out wobbely and thick, stiff, not good.
I finally knit a had with some lace pattern - for myself. I did rip that one out about 3 times, too.
Well, the string looks good. But I have not the least idea what would be the perfect pattern (drop stitch tunic maybe?) for it.
So that yarn I did rip out more then 10 times (compliments to the yarn: it did not suffer).
Good luck with your slippers!