Work and Unemployment
I once had a neighbor tell me there was no more work left to do on his yard. I kind of chuckled. Was there really NOTHING he could do to further improve his yard? Of course not. There is ALWAYS something more you can do. More fertilizer, flowers, a new pool, or even an amusement park addition as was the case for Michael Jackson. I'm sure replacing all the brick with gold bars would also be an improvement. You get the point.
There is no limit to the amount of work to be done. From your yard to space stations there is always SOME work which could be done. Labor is limited. Time is limited. Materials are limited. Work is not. Perhaps more important, motivation is limited. Limited by your perceived value of the product of your labor. It is human nature to balance the cost in labor with the value of what you receive in return. So what he was really saying was any further improvements to my yard are not worth further effort. It is this perceived value and the cost in labor balance which determines the work to be done.