I do approx 2 hours light tapping, gradually banging it harder with a mallet until the 4 hour mark. I do the whole face, with particular attention to the edges and toe. I'll then do a general tap around the bat to test the ping, looking for dead spots. If I find a dead spot, ie. a part of the bat that doesn't go as well as the ajoining sections, then I give it 10-15 mins on that spot.Some willow needs extra knocking in to come to life.
I then hit a few balls with the bat. Something like using it for fielding practise or throw downs give a good indicator of how ready it is. Couple of my players commented my latest bat could do with some extra knocking in on the toe as it felt a bit "dead" - so back it went. If you see seam marks across the bat, put it away and give it another 30-60 mins. Keep doing this until the face doesn't mark and you should be finished. I've done roughly 5-6 hours on my latest bat.
I oil before knocking in and apply a full face protective sheet after knocking in is finished, just to minimise damage to anything I've missed.
The more knocking in the better - but 8 hours is a maximum I guess.