Someone you find attractive, funny and easy going.

Someone you look forward to see, and not just in "I'm going to get laid" way.

Someone who knows what you like and has not problem with it.

Someone that can rock a pair of  6 inch stiletto shoes

 
As for having multiple ATF why not, This is what hobbying is all about.

thing as an atf for me. If she keeps me interested I'll repeat. If she lowers her rates I'll repeat. If she has fur I'll repeat and re-repeat

If it is there, I'll be back.

And yes, I do have multiples but they should properly be called "favorites".  There can only be one "all time"

That I really don't have one. All of my clients are my favorites. I can't just choose one in particular.

Both must want to have more sessions together.

I've been with a lot of women. Several stand head and shoulders above the rest, but whom I equally adore.  

I can't put my finger in it, but something happens that's uncontrollable. And I prefer to let it run its course ...  
I don't want to control it.

Each is different in her own way.
One is an anal nymph with 100(?) or so dates in the book  
One is just the sweetest gal that likes to fuck and suck and scream and cum ...  
One was (retired) the quintessential courtesan ... my first, and there is a difference
And my current ... I'm totally addicted... and this too is a first. My kryptonite. 😚💓😘

I'm not into the semantics of ATF and what it is or isn't. This is my view of the world
so it's 100 accurate and true ... for me.