Blades are very expensive and if you find you are having to replace them more frequently, try flipping your olfa mat. These are two sided though many people think you only have the side with numbers.
After a few years the plastic self healing mat becomes not so self healing anymore and can interfere with your blade.
You will have a fresh surface that may make your cutting much easier and more accurate.
When both sides are no good, do not hesitate to buy a new one.