12-24 hours, just be aware of the date they were gathered. I usually put them in a carton and prop one end or the other up, switching 5 times a day. That way the turning is already started.
Not sure of the logic of starting the turning right away, I'd guess a lot of folks don't. That's just the way I learned it.
Maybe??? it's to keep the air cell evened out?
I hope you have better luck with shipping eggs than I did. Post office was too rough half broken even though they were wrapped very well and none hatched too scrambled in transit.
Yes, let them rest large end up. When I get eggs in the summer, I put them straight into the incubator, but do not turn for 2-3 days. The eggs have been warm when unwrapping them, so why let them cool down again. So far, its working fine.