I've had something like that once. BBBJ with a provider, and the first pop was pretty quick and 'normal'. But she kept going. Within a couple of minutes, Bowser the one-eyed trouser schnauzer was tingling like nothing I had ever felt before, and like nothing I've ever felt since - it went on for about 10 minutes, literally so close to an explosion that I thought I was going to climb the walls. I was actually kind of afraid of what was going to happen when the scale finally tipped. I thought I might blow the back of her throat out or something. When I finally did explode, it was pure heaven...I found out firsthand what 'hurts so good' really meant.
Haven't been able to get there again, but I'd sure like to.