The "lean" way of working goes well when building new aircraft or cars but from what I have seen it's not well suited to major checks on old aircraft. All it takes is one airframe guy to pull up a floorboard and find heaps of corrosion and suddenly all your milestones and charts can go in the bin. And if your lucky you have leaned out your workplace so much there is no one left to do OT to fix said corrosion.