Make sure you are cutting with the blade straight up and down to minimize the 'grooving'. I seldom use the grid lines to cut anything except when I'm straightening an edge at the beginning so my cutting is not always in the same spot. I have a Fiskars mat that's almost 20 years old and still in great shape.
Here's info on the soaking of mats.
http://tulip-patch.blogspot.com/2010...-olfa-mat.html
And a review of the mat smoother - they do work, as several members here will attest
http://quiltersreview.com/index.php/...es-a-worn-mat/