Keep spares.. and alot of them if you plan on using your cutter frequently. I second the fact you need to move them over a smidge so the cut isnt in the same place every time. flip and turn as much as possible after every cut.. The white/clear ones are not self healing like our rotary mats but they are pliable.. they do dry out and get brittle after lots of use.. you can however buy bigger and cut them to size.. When my 10x10 gets pretty worn from my 10x10 dies I''ll cut it down and use it on the 5x10 dies.. Ive heard some Accuquilt users gently ironing them between a cotton towel. I have yet to try this but others have said it has worked.. You just need to test and figure out the heat level of the iron..