A bit off the subject here but since this thread is about cutting mats I would like to ask about taking care of self healing mats and how long should they last. I bought a Martelli maybe 4 years ago and it has several places that have deep grooves where many cuts are made. I thought these expensive mats were supposed to last a long time?? Is there a way to remedy this? I just am not too impressed with the Martelli. I had an Olfa mat that lasted a lot longer and actually is still a back-up.