I have cancelled dozens of works tickets now. Mostly because I'll speculatively book multiple departures when cheap, and take the one I end up needing.
I used to take the credit. And reuse it. But I stopped doing that because it's confusing to constantly track credits. I find it easier and cleaner to cancel and refund.
Plus, you should always want to put at least $0.01 of a ticket on a card with travel protection benefits like CSR. That way if there are irrops, lost bag, or whatever your credit card insurance covers you.