to getting older that can interfere with sexual performance. The first is stamina, and the second is keeping the equipment in good working order using whatever tools that work for you. A back-to-back is not too much different that a two-hour session with one girl, except that the second girl may not have had a customer during your time with the first girl, so she is not only younger than you to begin with, but she was resting while you were wearing your ass out with the first girl.
Stamina is a product of your overall cardiovascular health. There is no easy fix for this except good old-fashioned cardio exercise. This can range from walking 2-3 miles a day at a brisk rate to more intense activities like stationary bikes, stairclimbers, treadmills and rowing machines. These all provide a similar beneficial workout, some more intense than others. Training your heart muscle to perform at a higher level for an extended period of time is the most important aspect of countering the effects of age. Your heart is probably fine if you are fucking ladies your own age, but we all know that's not want we want. We want the younger ladies, and in order to hold your own with them, you should do cardio training until you have the stamina of a reasonably fit 35-40-year-old.
Are there other things you can do while you are training to get your youthful stamina back? Yes! There are supplements you can use to improve the oxygen levels in your blood that are also vasodilators. The more O2 in your blood, the longer you are going to last. Sleep helps, too, 8-9 hours the night before a 2-hour or back-to-back is best. I have had good results with powdered beetroot or beet juice 30 minutes before a session of two hours or two one-hour back-to-backs. Beet creates Nitric Oxide in your blood which boosts oxygen levels. Additionally, I will often take red ginseng extract in the car before I get the go-ahead from the booker. Red ginseng is a natural stimulant which gives energy without caffeine, a vasoconstrictor. I buy the little sticks of Korean Red Ginseng and take two before a session. 30 doses run about a hundred dollars. Unfortunately, smoking is also a vasoconstrictor, so is alcohol, so if you can hold off on these until after you are completely finished fucking for the day, they will not be able to interfere with your performance.
The other aspect is your performance, and ultimately your enjoyment of the session(s) is how long you can stay erect. This is partly linked to stamina, but I have tried various things that give me an edge when I feel I need one. On a one-hour session with one pop, I'm good without any help. If I'm going for two pops, then I will often take some sildenifil just before getting in the shower for a two-hour session. It starts working in about 45-55 minutes, which is after I have had the first pop, and helps me get through the refractory period faster in anticipation of the second pop. If the sildenifil metabolizes too quickly so that you are past the window of opportunity before the second hour starts, you can use trimix instead at the start of the second hour. (Don't use sildenifil and trimix in the same day, it's dangerous, so you have to reschedule and try over again, skipping the sildenifil and just using the trimix alone.) An older friend of mine does this with great success. He doesn't need trimix all the time, but uses it for an extended session of two hours or longer for MSOG, but doesn't take it until AFTER the first pop is finished.
Obviously, it takes time to build up your heart muscle by doing cardio exercise. But some of these other hacks can be worked in quickly and may improve your sessions sooner rather than later. The reality is that it's more effective to invest the time to improve your stamina, which in turn increases your blood oxygen and may give you firmer and longer-lasting erections. In the meantime, try to stay away from vasoconstrictors and embrace vasodilators on the days you hobby.
TRT can also reverse the effects of aging, but that is a separate topic for another thread, and has its own pluses and minuses.