How long for books to go live on Amazon?

[Denise]

Ok, so, you upload your book to Amazon and then hit "publish". How long does it take for it to go live for sale? I couldn't find this answer on the KDP help section, but they say up to 72 hours. Yikes! How long does it usually take?

If I decide to do the shortest ever preorder, when is the latest I can upload? 3 days before the publishing date?

I'm asking this because I'm going to launch without preorder, but since I already scheduled NL swaps and told my list about the launch date, I need to get this right. KDP help doesn't give an answer. 

[Writer]

Mine are usually live within 12 hours of punching Publish but there are sometimes delays. When that happens, it can take closer to 24.

Preorders: assuming the file you upload is your final one, finished and ready to go, you've got either 3 or 4 days. I forget which.

[TimothyEllis]

Mine usually go live just inside an hour.

[Guerin]

Mine are usually live within 24 hours, many times much less. I think it gets faster with the more books you publish and depending on the format you upload.