It's funny you say that because his very best work to my eyes is on old rusted steel or mildewed wood as opposed to a pristine canvas. His work is dirty and feels more authentic banged up. I understand the context to mint is generally prints and no, i don't believe that will become less of an issue. It will always be important to the collectors of today and tomorrow.
As for the supply of mint Warhol and Haring, there is plenty of it and while it may fetch a premium it's not an exponential premium to something in good condition. The premium is in the artist's name or image itself (in the absence of horrific condition issues). I remember a set of 4 Warhol flowers maybe a dozen years ago at auction sell for the same price as what one would expect flowers of that size to sell for at the time. Yet these were obviously hung in a kitchen at some point as they had food stains galore but it certainly didn't hurt their value and that's an image with huge numbers of paintings in various sizes and colors. For those that insist on mint anything that was made in editions of 150, it simply means their search will take longer and longer in the future as opposed to someone comfortable with a ding here or there who can live with it as is or take on a small restoration project.