Several montha ago I posted advice from a manufacturers Rep who said that to keep your mat in good condition for longer periods to soak them in warm water(in a bathtub) for about thirty to fortyfive minutes and then hang them to dry. This can be done every few months and by renewing the moisture it helps the selfhealing to take place. You can use just a few drops of dish soap if you wish but it is not necessary. I do an occasional scrub, dry, with a plastic scrubby like you use on coated cookware. This removes any fibers trapped in cuts on the mat when there is a lot of fiber in cloth or batting. I tried to turn the mat over when cutting batting butkept forgetting.
The Rep also said you could straighten your bumpy mats somewhat by placing them on a cement sidewalk or driveway early in the day in a place that will receive sunshine later in the dayand let it absorb heat and leave it there till the sun went down and then it should be usable again. Hope this helps you/