Lawnmower replacement blade

Hi,

I have a a LM2102SP and mowed my lawn sporadically for 2 seasons. It's gotten some rocks along the way and the blades are showing signs of damage.

How often do you all replace blades? What brand and where to get replacements?

Thanks to all for your help!

EDIT : Thank you all for your input. I'll look at sharpening methods and also have a 2nd blade in hand.