I changed my cancellation from moderate to strict (with grace period) in the middle of this year as I was fed up with guests booking with me then cancelling as close to the check in date as they could without penalty because they had found cheaper accomodation elsewhere.
I was worried that a strict policy would cause a drop in bookings (especially as I changed it in the middle of winter) but that hasn't been the case. Also the quality of my guests has generally been better than when I had a moderate cancellation policy.
I've only had one guest cancel a booking since I've had the strict cancellation policy & I let him know that if I could fill the booking he had cancelled then I would issue a refund. Lucky for him it was a popular date, I filled the vacancy and sent him a refund.