If some people accumulate lots of vacation, it just means that they put in extra hours of work earlier. They didn't inherit labor credits from their grandparents or triple their vacation balance through investment and speculation. But more than that, I think there is a real difference between greed for money and the desire for labor credits. Money represents consumption. Labor credits represent time.
Some people keep track of the time they work to the last tenth of an hour.
It's all on the honor system anyway. We fill out our own labor sheets and total our credits ourselves. Visitors sometimes see our labor system as too uptight, too regimented. But as Robert Frost might have put it, good structures make good neighbors. It's the structure of our labor system that allows us to relax, trusting that the work of the community is being taken care of and we are all doing our share.