I bought a big bag of them before I brewed my first CAP with about 25% flaked corn because I thought it would help with the lautering. So I've used them for this beer twice now but never for any other beer. I soak in the mash tun with hot water to : 1) Rinse them off, 2) rehydrate them so I don't absorb a bunch of wort, and 3) preheat the mash tun. Then I run that water off. So I don't include them in my grain bill for the purposes of determining absorption.
The last time I considered not bothering but since I had them I used them. It worked well and I had a nice easy runoff. But I'm thinking I could probably have gotten away with not bothering. The next time I brew this beer I'll probably just see how it works without them.