Buy an Oregon Blade, they last the longest for me and my chainsaw gets heavy
use! It's worth the 20 bucks, and really unless you work a saw like I do
having one extra blade should suffice. I only have two extra blades per saw,
I can usually use one blade for a whole season, I do sharpen it regularly
though, the spares are there in case of breakage and then they usually get
rotated out of play after a season. Basically I buy one blade a year and
always have two on hand.