I think heavy pressure dulls the blades faster too. I tend to be a "clencher" - I tend grip my pens and things with a death grip and use heavy pressure to write, and have had to consciously teach myself to hold things with a more delicate grip. I was doing the same with my rotary cutters, death grip and heavy pressure. Now I hold it with a softer grip and use less pressure and I swear my blades are lasting a LOT longer. My mat doesn't show the wear now either, instead of deep slices I make only very small slits in the mat and it heals up much better. My rule now is that if the blade doesn't cut well with light to medium pressure, I replace it. Even with that self-imposed rule (which means I'm always cutting with a delightfully sharp blade) I'm pretty sure I'm going through blades slower than I did in the death-grip days. And my wrists feel better too.
A tip that helped me remember to lighten up - I think it came from this board. Someone said you push FORWARD on the rotary cutter to cut, not DOWN. Obviously you still need *some* downward pressure, but that little saying helped me adjust my habits.
Hopefully some of that ramble helps.
