I recently completed a partial residing of my home using HardiePlank cement board siding. To make the long story short the folks at the building supply business told me that if I was going to make more than a few cuts with a circular saw (as opposed to nippers) I ought to buy a diamond tipped blade. I did, and the blade performed admirably. But at the very end of my project it seemed the blade was getting tired.
The blade was $19, which I considered inexpensive given the “diamond” aspect. But as I said, it performed admirably.
My question to those SDMB construction folks, is, when do you decide a diamond tipped circular saw blade needs replacing?