On occasion, I will meet a lady touring Chicago.  Typically, the lady will email me later apprising me of her future plans to return to Chicago.  While I appreciate the email, most likely I will not be repeating and thus the info. is of no value to me.  So what to do?

No reply is necessary. If you might want to meet up on a future trip, then a " Can't this time, but keep me posted on future dates". This ain't rocket science and at least the women are intelligent. lol

If they're not going to get your money I highly doubt any provider will care whether you get back to them. Only 1 out of 10 appreciate the good manners of emailing back, probably. I think most of them would be happy to have less messages to respond to.

Think about it, when a company or business you purchased an item or service from emails you weeks or months later, and you do are not interested, do you send them all a reply saying "thank you but I'm not interested?" Likely not. Similarly these wonderful providers are in the business of marketing and seeking repeat clients too. And many gentlemen do want to know when someone is returning. However if you not interested in repeating for whatever reason, then no reply is needed.  

1) You are by no means obligated to respond...

I tell them I was so happy to get their email because I haven't been able to see anyone new for awhile because I lost my job, but since we have a rapport already, and she knows I'm an honest guy, if she wouldn't mind floating me for a few months until I find a new job and get re-established, I would send her the money then, plus a nice tip to make up for the delay.  Can I book two hours? . . . . .

the same position as the OP, trying to figure out how to respond lol

I don't email clients or at least I try not to  
If my business is slow what I would do is post a discount for repeated clients in my ads or website
I have a tour page in my website always updated  

In the parlance of things, it is junk mail.  A solicitation for business.  There isn't time in the day to answer all the junk mail I get.  (We're assuming it isn't just a thank you note -- but on the other hand it could be as authentic a thank you as the Christmas card I get from my bank.)

I think both parties always reserve the option to respectfully decline. In this case I think you would be doing yourself as well as the lady a bigger service by replying and telling her while you had a memorable time you prefer to initiate contact and to please not send along her touring dates. You are not insulting or offensive in this approach. If the lady has a newsletter you may have unknowingly subscribed to, ask to please be removed.  

Do you answer the phone when you know it's someone you don't want to talk to?

Amazon damn near immediately wants to know if they fulfilled your need for what ever crap you just purchase.

I've only seen one touring provider, and she asked me explicitly at the end of the session if I'd mind her texting me when she's back in town. That seems like a good way to do it.

Agreed...even if you change your mind at a later date...the lady has been respectful in asking and will respond kindly when you ask her to no longer receive alerts of her travel plans!  

I rely heavily on sending out email notes to those who've shown interest and those I've seen. I advertise very little. 90% of the people I see, repeat and the only way to know my schedule is by emailing me or by me informing them.  

The email probably didn't make the op feel special enough, no discount, no offer of OTC, had the email contained something along those lines, the opportunity would be taken advantage of.

A reply that includes the phrase "I will not be repeating" can be hurtful and will most likely do more harm than good. A no reply is just fine.

My emails never contain those things. Whoopsie, looks like I've been doing everything all wrong. Thanks for schooling me.

Meaning, you say, "Oh I'm not going to be there until after you leave." "Oh, that's ok honey - I'm going to stay another day - we can do then!"

I wouldn't reply. If she even notices, she'll probably think that 1) You won't be around or available, 2) You're no longer hobbying, 3) That you don't frequently check your hobby email, or 4) That for whatever reason, you'd prefer to move onto other escorts (happens all the time).  

at least you're honest about it, but this is probably an unrealistic expectation

First of all, we are in the underworld of society. Anything and everything can, and does happen. Communication is a part of that. Secondly, I would have to take a look at how the ladies respond to my experienced requests for a date. Some ladies respond with flowery details, and personal information. Some ladies respond with just the facts ma'am. Some ladies respond calling you a different name than one you wrote down on your request. Some ladies delay their responses. One lady wrote me back a year later saying she was available. Some ladies don't respond at all. One lady sent me a blank email as her response.  

Do as my regular friends and I do....

I don't think there is a need to respond. As providers, we don't suit EVERYONES taste and that is OK. If she gets butt hurt about it, she is in the wrong business.

There are a lot of reasons someone may not wish to receive email from a provider. It would not insult me for someone to ask to be removed from advertising mailers.

Replying and saying, although we had a great time and I enjoyed meeting you, I prefer to hobby widely and mix up my experiences and I'm not looking to see someone regularly so please take me off your mailing list.
Just simp,e and effective and zero offence will be taken.

I WISH people were honest. It doesn't mean being rude, but how nice would it be to NOT send an email and save my own time if I know the client I saw once, will not repeat because it isn't his "thing". You can even mention it before you see her for the first time, so she knows regardless of how the session goes, your mind is made up. "Hey Jean, I'm super excited to meet you and spend time with you, I will be honest and mention that i kind of have a thing for seeing different women each time I do decide to hobby. But I'd just love to make a long lasting memory with you!