I've been ordering books from Ingram on a twice a week basis for years now. 

This week I'm switching to once a day, or at least five times a week. There is no reason not to. I can easily fit that amount of ordering into a morning session, meaning I'd get the books the next day. I've also decided to not order from Scholastic, Simon & Shuster, or Harper Collins unless I have some extra money to stock up at the cheaper discounts. They take much more effort to order, take much more time to arrive, and have completely unpredictable fill rates. 

I'll keep ordering from Penguin Random House because of their wide range of titles, including DC and Marvel material. It's also relatively easy to use and easy to keep track of how much I'm spending. But because they take ten days to two weeks for the books arrive, they will be my second choice on just about everything.

If Ingram doesn't have something and PRH does, I'll order from them. If Ingram only has it from the Tennessee warehouse, I'll also order from PRH, since it would take about the same length of time to arrive. I'll also order a quick copy from Ingram and perhaps a backup copy from PRH if the title is hot enough. 

Both our best year (until now) and the best month we ever had in sales I had dedicated to ordering mostly from Ingram and ordering often. I had a feeling that PRH might be slow this summer and decided to go with Ingram for most everything. As it happened, PRH's warehouse had problems and things took two weeks to show up. Because I'd gone with Ingram, it didn't hurt us.

I don't trust PRH not to have similar problems during the Christmas season. My guess is that they took on way more trouble than they expected when they took on Marvel comics.  

The sales were so much better in August, a record month, that I think the discount difference became much less important. So the fact that it's quick, easy, and predictable is much more preferable than the extra 10% or so I get from ordering from the publishers direct.

If the publishers ever get their act together and get stuff to me in less than a week, I might change my mind. Sadly, if I wasn't ordering comics from PRH, I'd get books from their Reno warehouse in a few days. But because I am, I get my material from a Westminster, New York warehouse. Kind of ridiculous that I can't separate the two things, but there it is.