What are the differences among SPD cleats?

[Ricitius]

What is the best cleat out there? What makes them better than the other? Sorry for my questions, I'm intrested.

I just got some Specialized mtb cycling shoes and put on the cleats that came with my Egg Beater pedals and am riding well in my commutes. I am wondering what the average life-span for cleats is? I am considering buying an extra pair just in case anything happens. Better safe than sorry I guess.

[Scotty_Dog]

I am wondering what the average life-span for cleats is?
Same as tires, chains, and brake pads........... it all depends on how much and how hard they are used.