... on a number of factors. The biggest is, have I seen the provider before.  I tend to see a few favs and occasionally someone new.  I know how long my favs take to respond under normal circumstances, and usually I know if they're out of pocket for awhile.  So depending on their habits and circumstances, I may wait more than a couple of days.

For someone I've never seen before, I usually make a request through P411 if the provider uses it.  I've found that I always get a reply back within a day or two, unless the provider is out of pocket eg vacation.  If they don't use P411 and thus I need to use email or (very rarely) text message to reach out to them, I'll wait at least a couple of days for their initial response.  If I've heard nothing after a couple of days, I'll usually move on.

That's a long way of saying I think your 48 hour policy is reasonable, given you book a week or so in advance.  

I should note I usually book at least a couple weeks in advance because I have few holes in my schedule so I want to be sure I can book the provider for a specific day and time.  But there's exceptions, eg if a provider has to cancel a date because of illness or some other reason, I'll try to make arrangements with someone else on fairly short notice.  

A funny anecdote on this topic:  I reached out to a well-reviewed provider via text message (her preference) awhile ago.  Never got a reply. I moved on, actually forgot about it.  Then several weeks later I got a cryptic text from her saying she was available that day.  I scratched my head and asked, "Who is this?" as I had no idea. She sent another cryptic message.  Later when I had time I searched on her phone number (she'd changed it since I contacted her) and found out who it was.  So I thanked her for reaching out to me but said I wasn't available that day.  Over the next week or so she sent me a couple more cryptic texts about being "around".  I didn't reply. And I blocked her phone number.  

Ladies, if you're reading this, IMO that's NOT a good way to respond to a respectful request from a prospective client.

If I get the booking form from my website usually 1-2 hrs because I already have everything I need for screening. When i don't get it.. it depends, screening would take longer.

...snd it's what I do.  
 Sometimes I'll send out a second email to ask if she ever got the first one ( it might have wound up in her spam folder), but with so many available providers I rarely do that anymore. If there is no reply after 48 hours then it's her loss and it's time to move on to someone else.

I respond to all communications within that time frame, but usually by the next day at the latest. It really depends on how busy my personal and professional schedules are at the time.. Anyway you sound like a dream prospective client! You contact providers with ample time to screen and schedule. The only inquiries I outright ignore are those littered with obscenities or vulgarities.. To be honest I didn't think hobbyists had issues like this. I'm still fairly new but I have found myself time and time again emailing or texting with prospective clients for one or two days just to have them string me along and never land on a solid date.  

In any case, it's always interesting to hear a perspective from the other end of the computer or telephone. Best of luck on your search for a reliable companion. If you're ever in Chicago I invite you to parouse my website and check out my secure booking form. I might be young but I am always conscientious and very through.

That is the one thing that really annoys me: all of the back and forth e-mails/PMs that ultimately lead to nothing and waste my time.  If I take the time to PM someone, it means that I have done my due diligence and that I am serious.