Personally i think it's the dryness/lack of moisture in many modern bats where the main issues are in terms of longevity, rather than the pressing. So I wouldn't spend hours knocking it in, but maybe a little.
I personally don't spend hours knocking a bat in, as would rather play it and get the maximum value from it. If you were to knock in a bat for hours to get it to what you thought was 'optimum performance', you'd be doing a lot of knocking and potentially shortening the lifespan of the bat imo.
Unless it has a flat face, sharp edges and hasn't had the edges boned, then imo it shouldn't need that much prep. A bit of knocking to the edges, toe and some throwdowns/gentle net and off you go.
If the cleft was dry to begin with, then no amount of knocking will help prolong its life.