unless you have left a message with a specific time frame that you would be free to answer the phone.

And the agencies I deal with usually do not return calls, especially to someone they do not know.  With an agency, if you do not get an answer, you can usually assume  (1) they are on the phone with someone else, and you should just try back in a few minutes, or (2) they are closed.  

One word of advice, do not call an agency with questions or to try to schedule within 5 minutes before or after the hour or half hour.  That is when they are the busiest directing guys to providers' rooms.  You are more likely to get a friendly response at, say, 20 minutes after the hour.

When calling an agency, you still have to
be screened. It may take up to 24 hours.
If you have been screened, maybe 2 or 3 hours.
If the lady is not busy.

I have not used an agency, but after 8 hrs, I would move on.  Indie, well, maybe 24 hrs, and I'm gone.  After all, they are busy, and not just sitting by the puter waiting for us, ya know.

Swim

How long should one wait after contacting an agency or provider before giving up and contacting someone else?

1 hour
5 hours
8 hours
24 hours

?

I'm not sure how agencies work but many providers book well in advance. I would give a provider 24-48 hours before moving on.

appointment that evening, you probably are SOL unless you are calling an agency (then call at 20 minutes after the hour as has been said).  Most independent providers need at least 24 hours to screen you.  

I generally try to schedule a date with independent ladies about a week to 10 days ahead.  I then give the lady about 48 hrs. to get back to me.

For one who takes mostly same day or next day one-hour appointments, about two hours should be plenty of time. If you do contact someone else, and then the first girl gets back to you, you can always suggest making plans for a later date.

The bottom line is to wait 24 hours, if I do not hear back from her or the agency, then it is okay to call another provider?  

Initial contact was by email as was the follow up contact sent hours later (5 or 6 hours later).

Every situation will be different.  Some gals will get back to you in a few hours, some in a few days and some not at all.  Even my favorite agency advises clients on their website that email bookings take 24 to 48 hours.  

Providers are not sitting by their computer or phone waiting for you to contact them.  They have chosen this life partly because of the scheduling flexibility that it affords them. Many of them don't respond to inquiries at all when they are taking time off from the job.

By the same token you are free to make as many inquiries as you like and choose whomever you prefer based on the responses you get.  Double booking and then pulling a no-show is never a good idea but simply telling a lady that you have decided to go with someone else because you didn't here back from her is fine.

In general, if you are looking to get laid in 24 hours or less your best bet is probably going to be an agency or a lady with a current ad posted on TER. The phone is going to be your best approach as far as contacting her if time is of the essence.

I would allow 2-3 days if it is an independent provider if you are contacting an agency I would say allow 24hrs.You stated you have already sent an email and a follow-up with no response I would give it another day and move on.Also,the lady that you contacted does she require screening info and if so did you supply this info when contacting her?Also,independent ladies are busy and things happen she might be out of town,does not reply to emails quickly,or just plain unavailable.If you stated a nice introductory email to this lady I am not talking the "Hey,are you available on this date?"and you still have not heard anything move on to the next lady if it has been past the timeframe I stated above.I always respond to an email within 24hrs even if I do not feel good or unavailable but not everyone is the same way.Be patient I am sure you will find the lady for you.
jaydalee

As has been said, I'd not expect to hear back in less than a day if you've not been screened.  Indies can take longer.  
There are some quick action girls that say yes to anybody who calls, takes the first one to arrive in & turns her phone off until she's available again.  They can not possibly screen well in that time & have the highest risk IMHO.  I'd not book one of those (read the reviews) as I'd be circling the call point having wasted my gas.  (I'm not the one to rely on luck.)
Did you give instructions about calling back?  Do you have a hobby phone?  Many will not return calls unless asked to do so & given a time frame.  
Did you specify when you'd like to meet?
If you are not reasonable about screening, they'll ignore you.
Did you mention anything forbidden?  We both know why we're there...  you should fully research, her profile, ads, web site (if any), reviews (yes you need VIP for this).  If no donation is listed, you can inquire but never mention anything beyond an appointment.  

Best Wishes,
skb

waiting period.

More than once I've had a would-be new client call me and leave a message because I couldn't answer right that minute (sometimes I'm with a client or I'm driving or whatever, etc.). Then when I called back (w/in 5 minutes to a couple hours), he's already called and booked another client who would see him immediately.

His excuse for it? "I wanted a lady right now and you were obviously busy."

One of the many reasons I stopped advertising on BP; too many men who wanted it "right now."

I contacted the agency by email with a 5-6 hour window between emails. I had hired a provider from the agency before, but wanted someone new.  The appointment was to be for a couple/few hours five days later.

I did receive a response. It is my assumption that the administration at the agency had a difficult time locating one or more of the girls I was interested in and finally got back to me with information.

It is a shame as I did lose over two days in my search and now can only give the next person I contact less than three days notice, but I believe it is well worth it since I do not think I burned any bridges with the agency.  

Thank you all for your help.  My worry was having two ladies reply with "yes" and then having to tell one I changed my mind.