I'm trying to convince myself that a blade per large project (instead of per year) is reasonable, anything over that is gravy. If I buy in bulk/on sale my cost per blade is under $2, that seems reasonable to use on $100 worth of fabric. The problem is I'm usually pulling fabric out of my stash and not thinking of it in those terms.
But I know the newness will fade. It's just so nice right now!
edit/ps: Ever notice how almost immediately after replacing a blade, you actually do go over the ruler or knick it some way that you usually never do? Only on the new blades...