I get evening upgrade (US Eastern time) emails only when booking a flight within my upgrade window. For instance, as a Chairman's, if I ticket 5 days out in the morning, I'll normally get an email about upgrade status in the evening. If they were actually allowing upgrades at 7 days out, I will get the upgrade in the evening. If I booked before the window opened, I get the first email at 7 days out in the early hours of the morning. If upgrade inventory is released later, such as at 4 days out, that upgrade always happens with the overnight process.