Good to the last drop LoL

..and I'm not sure what tour duration has to do with the experience a companion will provide. What I'm gathering from your post is that you might have been concerned that either of the two companions you were eyeing would possibly be too worn out if you were to book them for a session.

 
I can't speak for them, but being in a relevant situation, fixating on "volume" is futile. I've been away from home for over 33 days, and yes, I've had several sessions. I also hung out with other companions, attended really neat events, went out dancing, reconnected with non-industry friends, and got in some spa time as well as sightseeing. I've taken breaks for two or three days at a time. So no, advertising general availability does not mean one has had a session every single day during that time.

I'm sure she has plenty of gas left in the tank for you.
I'm assuming these are " agency" ladies?
If so, I'm assuming your concerned with " turn and burn-out? And maybe that her head is already on the trip back home?
I've beat myself up over this type stuff before. And then I just decided to go in there and make it great.  
Pick one, pick both. Or you can read her reviews for the last day of her tour...and they'll probably say she was at her best. And you'll be kicking yourself in the ass for cheating yourself out of the experience.

Very few hobbyist ask this out loud.  It's something I've always wondered, I know a guy who will not book a lady on the last leg of her tour for the same reasons you have.

Is she a party girl? Very few ladies are booked back to back for days on end. In my twenties and thirties, I was bullet proof. That would not have phased me. But now, I've matured. I prefer slow and steady.

Personally I don’t like the word tour!  Sheesh, Rockstars tour.  Now that’s out of the way, I have seen the same girl on the first day in town and the last day.  Big difference.  First day was full of energy and zest, last Day was tired.  The other thing I find to be the most solid statement in this hobby is YMMV.  Some ladies travel for bear ($$$), while others combine and balance.  In general I find visiting ladies do get tired and it shows.  You try 15 cities in 30 days.  Travel is tiring.  As someone said go for it because you never know.  Over the years my best experiences have been in their home city, mine or theirs!  In general, visiting ladies are not as concerned with repeat business as they may on come back once per year.  My .02

Did you think she was a virgin at the start of the tour?

I toured 2 (3 days max) nearly every week.  Even with 4 - 5 days back home recharging I was tired and ready to come home at the end of my trip.  I can't even wrap my head around traveling for 45 days straight!  How do you even pack for that?  LOL