Good to know! My aged cutting board has developed a bit of a blister in the middle, it no longer lays flat and I will be replacing it shortly.
Your cutting boards will wear out faster if you use the lines on them because you will start repeat cutting over and over in the same spots. It's the advice I give every beginning quilter and turn mine over and start by using the back and don't move to the front until I have to. Typically I have my fabric in some sort of angle to minimize the chance of repeat cuts.
Those deep grooves you wear into the markings by the repeat cuts will also give you skipped threads eventually when you cut across them.
Use the markers on your rulers, not the mat! It takes awhile to get used to, but once you do, you never look at your mat again and they last much longer, not to mention still being able to use both sides! If your ruler isn't long enough, well we have two ruler techniques, so you measure over with your long 24" ruler and place another ruler to the left of your desired length for your cut.