It happens once or twice a month, on average. The hold is now 12 hours instead of the 24 hours from a couple of years ago so it seems like an improvement.
Though very frustrating, I usually just let it play out because I don’t have 6 hours of energy to give to Airbnb. I’ve never been successful in having them open the calendar before the 12 hours is up anyway. However, almost always the guest is booked and it’s over with within an hour. If someone really wants to book, they do the verification and it goes through. You should at least give it an hour or two before you get annoyed or bother calling.
In my experience, if it’s blocked for the whole time that means you’re not getting a booking out of it. Sometimes people withdraw their request instead of verifying or withdraw even if they do the verification, but Airbnb doesn’t open up your calendar when the guest withdraws their request, you don’t find out until 12 hours later when your calendar opens up and it’s still empty. That’s the worst part.
And even though they block your calendar so that guest can get verified, they don’t make sure that the guest is going to be able book with you otherwise. Sometimes it’s someone that wants to bring a cat or something and I’m not taking their reservation anyway. This summer, my calendar was blocked for a few hours and it turned that it was a group of 4 for my 2 person listing. But most of the time it works out and works out in an hour or two.