The ideal window for me is 24 hours in advance, because longer than that i am unsure about transport, hotel (if needed) and other things. Less than that, same apply but in reverse, may be too late to book all the other things i need.
In a perfect world a schedule would be posted by every agencies, indies, and would be hold to at a 99% rate like any other job (cancelling only for illness or family emergencies) but sadly thats not how this business operate. The number of times i got a text while in the car or bus saying "she canceled" or "she don't answer..." It seem to be worst to handle these days. Not because they cancel more, i think this never really changed, but because the choice for Plan B is extremely harder. Too much day or early evening shift now compare to 10-12 years ago where lots of SPs worked til midnight-2am, so if you get cancelled at 2pm, you likely have half the rosters already gone or soon done (ending at 5 or 6), most of the rest are already fully book (some even fully book right as they open the phone at 9-10 am). Indies are much more expensive now and require much more to book (24h advance notice, screening, deposits etc), honestly nowadays its like you better plan a double booking, like 1 in the afternoon around 2-3, and one in the early evening, and hope AT LEAST one of them make it. Its not even a rare occurance that both would cancel. I assume indies who ask for deposits are more likely to NOT cancel themselves but its a step i am not yet ready to make. Maybe one day. Maybe ill HAVE to one day. But for now, i prefer to stay with good old cash.
Last time i was in Montreal i had about 4 cancellations in 2 days and a string of the worst luck there is, like missing a text from someone i had sent one the day before while being in the movie theatre for TWO FREAKING HOURS. Im not even kidding you. Like at that point i wasn't expecting a reply anymore, and then i finish my movie and boom see the text wich was sent about 15 mins after the movie started, i almost jump in the theatre (on my way out, not in the projection), but then she tell me since i didn't answer fast enough she made other plans.
. I couldn't believe it how unlucky i could be at that point. If i had decided to watch the movie a different time, i wouldn't had missed the text.
I was there for something else and i was not in a hurry to leave (staying at friend's place, so no hotel checkout) but at some point i was not gonna stay there for a week... I eventually got VERY lucky to have a meeting. I didn't review cause she asked me not to (she don't like reviews and it was positive, so i agreed to her wish), but basically it was either i do this booking or i end up going back home with blue balls, so i took a chance, i had a good experience with the agency before, and the SP had a look i like by the pics and was listed as "Full GFE", wich for them mean CIM pretty much, so i was like "ok...at that point, even if she end up facially average, im just hoping service is good. I very rarely go blind into meetings (without at least a few trustable reviews or if not a face pic) but i wanted to have fun... Turned out she was pretty and the service was good. So it did ended well. But the whole point to this brick wall of text is that if you only plan one booking and get cancelled, its very unlikely you manage to see someone else "on your list" from the agencies.
Thinking of it, i do think the incall being so dominant these days really changed the dynamic of the scene. Because when everything was outcall back then, guys couldn't always booked when they wanted, they had to rent hotels or host home (some not liking this). Incall made the whole in and out so easy for business men etc, they can just pretend they have a meeting somewhere or an errand or whatever, go in, spend an hour there, go out, no trace at all. So incall coupled with daytime shifts i think are to blame lol.
Obviously this is trough the perspective of a customer who had to go to the city. I understand for locals and especially SPs its great....