I once had the pleasure to fly for Lauda Air. Well , the pleasure was the actual aircraft. They were the cleanest flight decks ever seen. A 7 year old 737 had a floor you could eat off. Paint brushes everywhere , the slightest paint scratch professionally 'airbrushed ' out , daily hoovering and woe betide any crew who left it at all scruffy , or with fingerprints anywhere. It felt like flying one 'out of the box ' everyday .
It was akin to Niki lending you one of his Mercs/Ferraris and so on ............ The aircraft were also his babies.
It is quite easy to keep them so from the start. Discipline.