In that situation, nearly all ladies have given me vigorous hand work or mouth work to get me back up.  Sometimes it works.

I keep a goody bag!

I have a bag full of tricks if I can achieve anything with just me. Everyone is different & as we get older we need more stimulation to get aroused. Cock rings, penis pump are items I recommend if you have not tried them. Online adult toy shopping has made it easy to try new fun options.

Change to eating her pussy and it will relax you or make you excited again.  That usually gets me hard enough for round two especially if  round one was a bj.

What the old muffdiver  said will do the trick every time.

Simple answer to this question is who cares? Remember why you're there and who's paying for the time ... you're spending time with a gorgeous and charming girl. Caress her, kiss her, talk to her, tease her ... LOOK at her. Ask her to walk around the room showing herself off. Your performance is not important, hers is. The second you start worrying about how you'll perform with the escort is the second you start limiting your enjoyment. Store your experience in your mind bank and you'll enjoy her over and over in the future while alone.

Many good suggestions made above.

My personal situation usually goes like this...

Often times, my lady friend has orgasmed numerous times at this point, and is almost to the point of being over-lubed.  

And at the same time, I simply run out of energy, being 2 or 3-times her age.

If I can just catch a brief rest laying on my back, perhaps cuddling with my lady friend just soaking in the glow for 10 minutes or so, I can usually get back in the saddle to finish the ride.

Granted, this is with a dose of 40-60 milligrams of sildenafil, but I seem to almost always run out of energy all over, and that brief rest without stimulation seems to help things work again.