The most I've had in one sessions was 43. I'm hyper-orgasmic, and my husband is an engineer, so we took an entire day off to experiment. It gets hazy near the end - apparently I fainted a few times. It took about two hours, and was definitely way too intense to do often. At the end, I was laughing, sobbing, unable to move, and seeing lights. He brought me dinner in bed after I finally calmed down.
Usually, when not trying particularly, about 5-10.