I recently bought a Forrest WWII blade for my table saw. I'm very pleased with the cuts, but wondering how long it should last before it requires sharpening. Today I made some cuts in 8/4" hard maple and my saw was seriously bogging down. Is it possible the blade just needs a good cleaning, or am I just kidding myself and in dyre need of a sharpening?

Granted, I've been doing some heavy duty cutting, but I was hoping to get more life than this out of it. Since I bought the blade, I've made three cutting boards from 8/4" hard maple and walnut, cut a few pieces of 3/4" birch ply and cut some pine here and there. How much use should I expect from a WWII before it's dull?