So, should I tell folks launch day is 7 business days after I'm ready to publish?
Seven days is a looong time to wait. Your ranking will plummet, and you'll lose a lot of potential sales over delays that
might happen, but probably won't. At least, not to that extent.
I think those timelines are KDP's "cover their asses" strategy; Tim was right that 2 to 7 days is their default position on everything.
FWIW, here are the timelines I've experienced:
Covers: right away
Paperback to Ebook: 2-3 days
Look Inside: within 2-3 days, with one exception that took 10 (Amazon apologized profusely before I'd even filed a help ticket - very pleasantly surprised on that one!)
Time from Hitting "Publish" to Book Going Live: within 6-18 hours. I get so anxious during this process, I've taken to hitting "Publish" before I go to sleep. The books are usually live when I wake up , so I sleep through my stress

Anyway, Tim was right: you can't control any of these things, so try not to worry over them. Easier said than done, I know, haha. The important part is getting that ASIN as soon as your book is live, so you can start promos/announcements and get sales coming in. Congratulations on finishing (or being close to finishing) your book! Fingers crossed for you.
PS: I'm still pretty new myself, so feel free to take my experiences with a grain of salt if you want
