Thanks for the comment - this was the question I most wanted to understand. I realize that durations are on a continuous scale. I personally know people who operate across the full range of durations.

But it's still far from clear to me that grandmothers (aka entrepreneurs) see any liquidity benefit from folks with short holding periods. I'm not saying it's a problem if grandmothers like me dont see a liquidity benefit from HFT. I'm just asking if it exists.