It really depends on your place, @Isa11184 . Is there a good chance that December cancellation will be booked by someone else?
Here, there are a couple of things going on. I want guests to be able to cancel easily for a weather event, as we sometimes find ourselves dependent upon weather for guest happiness. 🙂
Also, our dates fill up very quickly. Cancellations take no more than a day or two to get filled, so I'm not out anything, or much, if guests cancel for their own reasons.
A flexible policy works well for me.
I do completely understand all those with firmer policies. I used to feel, with guests seemingly always claiming extenuating circumstances, that it was a lot of drama for little reward, but now that Airbnb has cracked down on that, I think it makes sense to at least go with a moderate policy so that you aren't always taking the hit for guest cancellations. The firm one if you need it. Few of us are in a position to act as travel insurers, and it is good to be able to choose what works best.
Hope that helps a little.