@Jennifer2682 I don’t believe anyone suggested blocking off a calendar. I do agree with you that guests should educate themselves about policies, and look for policies that fit their needs. However, the OP is asking about extending the initial 48 hour cancellation window in some way, as a favor to the guest.
As an aside, I have of late been using the “Firm” cancellation policy, in which guests get completely free cancellation up until 30 days before check-in. This is a new policy that gives guests some flexibility if they want to book a couple of months in advance, and for many locations gives the host enough time to rebook (30 days) if the guest cancels.