Provo Craft recommends 30 to 50 cuts for each mat. I have one and have used it hundreds of times. And I going to keep using it until I wear a hole in it! I spray it with a quilt basting spray every hundred cuts or so, to keep it sticky. I also clean it with baby wipes when it gets fuzzy. But I think most everyone knows those tips.
I trimmed the bottom (shown below) just under the numbers, &, yes, I know my trimming is kinda squiggly *smile*. The top I trimmed to the middle of the arrow. Whatever fits best on your machine though.
I also finished a new necklace with white and silver marbled beads...