[Excerpt | Valdor: Birth of the Imperium] Turns out that the Custodes have the phrase "If you have time to lean, you have time to clean" baked into them at a genetic level.

Towards the end of Valdor: Birth of the Imperium, Constantin Valdor is reflecting on the sense of enhancement and power afforded him by donning his armor, and his thoughts subsequently begin to go in a more meta direction:

If he had been capable of arrogance, he might have reveled in the results. As it was, he had not had a single arrogant thought since the dawn of his new >life-state. He had never taken pleasure in his capability, nor his equipment, only a kind of blunt satisfaction when an obstacle was removed, or an order >followed, or a threat dispatched.*
  *And yet, there were half-memories – dim ones, like snuffed candles – of the time before. He almost remembered what it was like to dream his own >dreams, or to feel the hot spikes of jealousy, rage or avarice. They had become intellectual constructs, those emotions, but still they were far from >unintelligible. In rare moments of introspection, he found himself wondering how much he had lost in order to gain the powers he had, and whether the >bargain was one he would ever have made himself, given the choice.
  Such thoughts did not last long. Every fibre of his being was set against them. Within moments, the obsessions would crowd in again, and he would >attend to his fine armour, and attend to the mastery of his superb weapons, and attend to the condition of his already superlative body. As he did so, the >old words would cycle through his mind, over and over, like a mantra of one of the religions he himself had helped to scour from existence.

• "If you have time to lean, you have time to clean" *

Kidding with the last bit — the actual quote is "You are the bringer of the new age. You are the warden of the old. You are the destroyer. You are the preserver."

That said, we all already knew it, but this is more evidence that Jimmy Space is a worse boss than your average Burger King shift manager.