We used to hear it was necessary to gradually introduce new shoes into your routine, as if shoes were like a new runner who needed to not do too much too soon for fear of breaking down. That’s not necessary. Structurally, new shoes should be good right out of the box for however far and fast you want to run in them. (They better be, given their price!)
There’s a difference, though, between new shoes and a new model. If your new shoes are fairly different from shoes you’ve run in recently, then have your first few runs in them be shorter, easier efforts. Two reasons for this: First, to see if they’re different enough from what you’re used to cause small problems, like irritation across the top of your foot or calf soreness from having a lower midsole. Second, so that if they are initially irksome, you don’t ruin a longer, more important run.
But if your new shoes are the same type you’ve been running in (whether that’s the exact same model, an update to an earlier model, or a different brand that’s similar in construction to what you’re used to), then have at it. I’ve had 20-milers be a shoe’s initiation rite.