Hah I have the opposite problem! After so many years of practice and edging, I last much much longer even than I want to in an AMP setting. Example, I go to provider last night, and time expired! She was super embarrassed and wouldn't shut up about it, like it was her fault or she wasn't sexy enough, but I was grinning ear to ear! The edging was awesome and I enjoyed every second of it. Sometimes the girls look like their arm is going to fall off! Mostly because many don't know how to give proper HJ, they just go for the jackhammer and think this will do it.
As far as chemiclas, I slam one of those C4 drinks they sell at the Wawa, in the parking lot before I go in to the AMP. Rock hard the whole time, and cum within the appropriate time frame. I guess the chemiclas in the drink are vasodilator and get the blodd flowing just right. I heard these work for ED too, man who works for me complained of it when I recommended an AMP for him to visit, he tried that drink, and had best cum of his life.