Hubby varies a LOT. I know tricks that speed him up if I want. We also have learned some ways to slow down. He has actually gone up to 45 min one time. I was so worn out. lol Guess I need to get into shape.
But it varies so much depending on the stimulation, and how turned on he is simply by the situation. Age seems to have an effect too the older they get the more they understand their body and can make it do more of what they want - Usually.
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"Always learn the rules so that you can break them properly." Dalai Lama
My Karma just ran over your Dogma.