You may better start your first churn now. But your second churn should be at least 6 month apart.
Agreed, eventually you can get on a 90 day cycle but I would wait at least a couple of years. Most of the people that are on 90 app cycles have 10+ years of credit history, and they also have a solid base of cards that stay open to help with their AAoA.
Saw your post after I posted, you need to shut down credit apps about a year before a mortgage app.