Thats exactly the reason I stopped advance bookings they done it to me several times do not show or get back in touch , so I say book on the day if they want  me unless we already met before .
Sometimes they sound genuine but end up to be arseholes .

Yes I do the same unless it’s a reg. I either tell them to get in touch on the day to book or if they are adamant about booking in advance take a deposit

Set a rule that they have to confirm by x am and if they don’t, book someone else in.

I tend to give 9am deadline for 11am bookings
And 10am deadline for the rest.

This way it gives enough time to find someone else as replacement. Works 99.9% of the time, have to be truly unlucky to not find a replacement.

Yes 2 hrs prior for early morning bookings, or by a slightly later but before 9am time for any other time advance booking.

Get a deposit, then tough shit if they cancel. Sometimes even a mention of a deposit will weed out the flaky ones. I used do this and then any hesitation would ring time waster alarm bells. Now I take deposits along with a non-negotiable agreement to confirm by 10am or they’re cancelled without refund. Decent clients understand we have to do this because of the time wasters, and I only do this for their first appointment. Otherwise you work your day around their time and then it cocks up your day and pisses you off.

Yes I forgot to mention that I might still accept advance bookings for regulars (someone who has seen me more than twice) but even in that case, I generally get about 50% of cancellations from regulars like literally happened again last week where this guy whom I've seen 3 times before booked 2 days in advance and literally 2 hours before the agreed time on the same day, the guy told me that his work schedule has changed and that he can't make it anymore  (I'm sure if I hadn't sent him a message to confirm he was still coming, he wouldn't even have told me)

But this idiot doesn't realised that he also messed up MY ENTIRE SCHEDULE on that day as well (I declined a few potential genuine bookings because of him). I was mad honestly 

Will probably tell him that if he wants to see me again after this, he will have to bring the 1h fee + 50% of the 1h fee extra for messing me around 

That's why I think that I won't even take advance bookings from regulars anymore, I just feel that because they are regulars, some of them feel that they have the right to be flaky and mess you around, like because they've seen you before, they feel like you won't be as mad if they cancel their booking at the last minute or do some carrot dangling

For pre booked bookings I always tell them to confirm me by x time. If they don't I will take something else.
Yes people will confirm me later sometimes and If i didn't filled that space i can still see that person, otherwise i will text back and say "I told you to confirm me by x time, you Didn't and I took another booking". I ask regulars to confirm me as well. Nothing is for sure this days.