Your comment about the relationship between quality and time reminded me of the law of diminishing returns, that's all.
As for "rendering", that would be represented on the vertical axis since it can be considered an "input". So you can imagine as the vertical axis goes higher, the quality of the renders increases. Time is represented on the horizontal axis, so the further to the right you go the longer the time.
I bring this up as part of a general discussion about L&P's development cycle. Many of us, myself included, enjoy the high quality of the game's renderings, and are ok with a trade-off of longer development cycles. But at some point things fall out of balance. Using the chart as an example of diminishing returns, L&P is putting in more and more time to improve the renders, but he's at a point now where he isn't getting the return on investment that he once was. That's my ultimate fear for this game, that L&P is the kind of person who will work twice as hard and twice as long, even if it means getting half the result.