[ignu]

This was a decade or so ago, but we used to get a list of ~2 million email addresses that we'd import into a new database and a single mailing would take anywhere from 2 to 3 days to complete. Sometimes it would take us a few days to get to it though.

The one to two weeks lead time always made a lot of sense to me.

(And yeah, you don't need to tell me how horrible everything about that process is... but it worked and no one's motivated to fix it. I wouldn't be surprised if that's the same process they're using today)