Rock Auto buys out over stock and closed warehouses a lot, that is how they get low prices.
I generally don't buy things from them that are prone to require warrantee service or replacement service. Those things I try to buy locally, even at the higher prices. Getting a core refund can be a challenge as well, at least it has been for me..

You will notice that Rock Auto usually has 3 levels of parts quality, The economy version is really cheap stuff, I would avoid if possible. The daily driver stuff is pretty decent and has proven to be pretty good stuff. The highest quality tends to be better, but not always, and surprising may actually cost less. They also have closeouts on parts they will no longer offer. They can be a real bargan, but you will probably not ever get a replacement part. .

They also have 4 warehouses they ship out of. Not all parts are at every warehouse. Some things on your list may come from 2 or 3 of their warehouses, and you will have to pay shipping from each. There is a way you can get most of the stuff from a single or maybe 2 warehouses, if you would allow substitute brands of the parts you order.