Like everything coffee-related, there's no simple answer since we're dealing with an organic product.
I have no experience of your machine Joseph, your coffee beans or your coffee style. So I'd say experiment.
A long preinfusion can help preserve puck integrity, especially at high doses, and thus help prevent channelling and underextraction. It may however also mean you have to back off your grind a bit to avoid choking the machine.
It can also help tame the brightness in certain single origins.
That said, some beans work best without preinfusion and it's generally not advisable for classic ristrettos pulled on single baskets.
Mike, "back off your grind a bit" dose weight?
Sorry! Grind a bit coarser was what I meant. But you're quite right: if you find that the grind you are currently using is giving you the taste profile you desire, stick with it and dose a little less.... assuming that increasing the preinfusion is slowing the flow more than you want or causing channeling.
Joseph Robertson said:Mike, "back off your grind a bit" dose weight?