It depends on the bat and the willow.A bat from Tim Keeley can largely be uses from the wrapper.A butterfly bat will need lots of oil and a load of knocking it.It just depends on the bat, who made it and how it was pressed and how patient you are.
Why does butterfly need more knocking in ?
Short(ish) answer. Try and avoid knocking in someone else's bat. It probably won't be good enough and if it cracks (no matter how careful you are), he will probably want your blood. Tell the lazy bugger to do it themself.