DAZ has the BEST online order history. It warns you if you put an item in your cart that you have already purchased.

I'm sure I'm like a lot of folks. I've purchased tons of stuff from several stores, including 18 pages of items at CP (mostly free stuff at CP) . I do not have a spreadsheet of my purchases. And even if I did, I surely do not want to check this sheet everytime I want to buy something from a store to make sure I have not bought it already, and there is no way I can remember what I've purchased over the years. I therefore rely on the store order history, which I do have to check from time to time, especially when older stuff goes on sale, or the bundle deals, and so forth.

Humankind has not woven the web of life. We are but one thread within it.
Whatever we do to the web, we do to ourselves. All things are bound together.
All things connect......Chief Seattle, 1854