A buddy gave me a pack of new blades that X-Acto makes. They are just like #11's but the cutting edge has a gold tint to them. I can't remember the name (X-Acto Platinum or something). These blades stay sharper longer. I've had the same blade in now for about two weeks and it is still as sharp as day one. I think they're great, FWIW. I'm not sure if they are any more expensive than normal # 11's since they were given to my buddy and he gave me a pack.
Try them out and see what you think.
Later-