Though I will say I'm not as easily annoyed as I see some ladies seem to get.
I don't really get worked up over people sending me an email in the morning for a late afternoon or evening appointment- if you are emailing me at 9:00am for a 3:00pm time the same day it's not a huge deal.
I am annoyed by people who perpetually ask for appointments within the time frame you mentioned (2 hours or less),
Not to be critical of you, but the whole "my schedule is unpredictable" excuse gets really abused. As someone who is also busy, I sometimes look at this type of comment as an indicator that someone is a bit irresponsible and flippant with their schedule/life. We all have a million things on our plate. Are you seriously saying you're not able to build in an hour or 90 minutes for a single day of the week? For most people that's just not true. Though some people have careers that are certainly like this (a gent I see sometimes is a repairman, he gets calls all times of the day). And at peak times at work, even my schedule gets this way.
But I also feel like the clients who most often send me the last minute requests are the ones who haven't read my website to even see my rates (because they are blasting requests to several ladies at random, since they are willing to see just about anyone). Too often, a request to see me in 2 hours or less is followed by an email saying, "how much is an hour?"
I will also note that a last minute request without sufficient information, with a special request, or for an outcall is what would annoy me me.
I understand wanting to confirm a provider is available at the last minute before sending screening info. But if you are emailing me for a same day appointment, you need to be ready to respond with all of the information I need to screen you as soon as I reply. I would also refrain from using references/whitelist/okays as your screening; there's no guarantee your reference will reply in a timely manner and I personally reach out to the ladies who sent the whitelist/okay for a person trying to see me.**
**the caveat there is that not all providers check in on this, some ladies just look briefly at who gave the whitelist/okay and are okay seeing the client
If you have a special request or fetish, there's probably more preparation that is required that makes a last minute request impossible. I got a request this weekend for something that I usually start dieting for days in advance.
A last minute outcall is also hugely inconvenient.
There are certainly ladies who are happy to see people at the last minute for any or all of the above and don't have the same time or screening restraints that I do.
Best of luck!