Well, I agree with the concept, but my cutoff is at 45%. I guess we all have our own cutoffs.
On some less expensive books, say for Open Road Media in India right now, having a bunch of lesser codes can still be nice. I can put a bunch of inexpensive books in my cart (now that I've figured out how to find it, with help from mitford13 and mgbino

), enter a bunch of the lesser discount codes, and make one purchase from my cart. Since I'm using the codes on inexpensive books to begin with, I don't lose that much by not using a higher valued code, and this saves me hassle doing a bunch of checkouts, and keeps my credit card company from whining at me too, which is also nice. I did exactly this just this morning.
Anyway, to each their own...
45%: 5TQsNu, 6kQDLy, 6kYi6Y, 6KsPGL, 6L9Uhd, 6yDZIA, 6YGpKp, 6YgzZt, 7xQsTA, 7y2GLs, 7Yd2se, 7yGdAI, Bt8vbc, bSf5KP, BSkatj, BsN8LV, bSRdm2, BSSpAv, bSuyCK, bsXiCP, bt4TNY, bT6N3X
55%: BWIL6h, BWJDFi, BWpUtW, bWrtNa, bwWpcd
65%: 5JyaYs, 6m6wsF, 7yLF8p,