They aren't expensive, and the difference sharp blades make to a lawn
is very noticeable. I was guilty of pushing my blades to the limit
when I started out, but I soon realized that for the small cost of
replacing the blades regularly, I could keep the lawns looking sharper
Which brings me to my next point: when choosing a mower, make sure the
blades are easy to change, and cheap, and readily available. I loved
the Honda as non genuine blades were extremely common and very
affordable. I ran 2 blades instead of 4, it just seemed to cut better
that way. And when I kept them fresh (new blades every 2 days or so) I
was a lot happier with the finished product.
I never actually bothered to sharpen the blades though. I have heard
of guys doing this. I preferred to replace them as the time taken to
sharpen them (say 20 min) wouldn't be worth the $4 it cost just to
stick new blades on.