I first contacted a provider via P411 on Thursday morning for an appointment the following Wednesday.  Her 411 profile stated that contact through 411 is acceptable.   It is now 4 days later, and I haven't gotten a reply.  I'd like to see this provider, but I'd also like to reach out to another provider for that day.  Have I waited long enough?

If I were in your position, I'd contact the second lady today.  Heck, I probably would have done it a day ago just in case the first one took too long in getting back to me. I usually go with a back-up plan anyway, just for the reason you state here.

Does she list a phone number in her post?  For some reason, many depend more on their phones than online contact.  While some ladies even list email addresses on their profiles, have noticed many don't check email as often as they do their text messages.  Not sure why.

What I would recommend in the future is to contact the next lady by email but also contact her through p411 as some ladies check their email more frequently. Just a thought.

I always wait at least 72 hours for a response, as some ladies have so many other things going on in their lives and some just need a break from their sometimes voluminous inbox volume. I am not telling you what to do of course, for if one day works for you, you should stick to that. Speaking for only myself, many ladies get back to me 2-3 days after initial contact but most return my inquiry within 24 hours (or less) when they are active in the business.

At the end of the day, this is just a service for hire situation and you have similar situations in other consumer areas.

You'd simply be having those great experiences with the women who replied to you in a more timely manner.  

Although companions allow contact through many different methods -- quite often they will let you know the MOST preferred method with the fastest response; be it her website booking form, email, text message, and yes - p411.

contact her now.

24 hours if they do their own booking and 24 minutes if they are represented by an agency.  The only reason it should take more than 24 hours is if she booked a multi-day date with one of her regulars, or if she's traveling on a FMTY booking.  If she's on vacation and away from her business (everybody deserves a vacation, right?) then she will most likely contact you when she gets back and explain.  Then you can still book when she's back.    In the meantime, see someone else until she gets back.  There are probably more providers than you will ever see in your remaining lifetime anyway, so there's no need to become really invested in any one girl.  

Thanks to all of you for your input on this subject.  It was all very helpful.  I've decided to go with plan B.  

I usually book about a week out also. If I don’t hear back in 2-3 days, then I assume she’s not interested; especially if I’ve seen that she has logged into P411 since my request and/or has viewed my P411 profile.