No, I don't. I tested a recipe for a friend a while ago that specifically called for sifting. That may be the only time I've ever done it. I usually think about trying it just as I add the last of the flour or I'm just too lazy.
It probably gets some more O2 into the dough which helps the yeast. It probably also helps with water absorbtion. With a long ferment, I kind of doubt it makes a meaningful difference, but I can't say for sure.
Sorry I can't be more help.