My own experience - I currently work slightly odd split day, 7-10 at home, then go to the office for 10:30, then leave at 4. This means that the postie almost always gets to me before I leave for work. They've never not knocked and just carded - if I get a card, it's when I've gone out before they come round (because the card isn't there before I leave the house). I get quite a few deliveries too, so I have a reasonable sample size.
Obviously, though, these things aren't consistent - after all, some people find Herpes and Yokel to be good couriers.