I have used all 6 - 7 x 17 holders in one day for sure, but never more than one exposure of the same image. But I almost always take the 8 x 10 and 7 x 17 and will use both on photo outings.
Since we have added other than ULF, I have to agree with Scott and also Phil Kember or Death Valley Phil. I like the format combination of 8x10 and 7x17. The most organized I have been was at Bill Schwab's northern MI Gathering last June with an 8x10 on tripod and a 7x17 on tripod laid out in the back of the SUV with the Baby Jogger bungee corded onto a trailer hitch 2'x5' basket that most people use to carry a dead deer.
I have added two 7x17 holders since my earlier post.