Your Normalized and Differentials Lenses power should steadily reduce in power over time. (+0.25 for myopes, -0.25 for hyperopes, moving towards 0) Being a quarter diopter weaker than what you need to see clearly provides a slight Blur stimulus for change. As your eyes improve, you will need to reduce again to maintain that slight blur. These reductions typically occur every 3-4 months, and should alternate between differentials and normalized with 4-6 weeks of adjustment period between changes to your focal plane. It is important to be sure you are ready to reduce and that your measurements justify reduction. Reducing too soon is never a good idea (see blur adaptation). Also when you introduce a reduction it is best to perform a "zero diopter reset".